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A  PRACTICAL  TREATISE 


MECHANICAL   DENTISTRY. 


Valuable  Works  Connected  with  Dentistry 

PUBLISHED   BY 

LINDSAY    &    BLAKISTON, 

PHILADELPHIA. 


HARRIS  (CHAPIN  A.),  M.D.,  D.D.S. 

The  Principles  and  Practice  of  Dentistry.  Tenth  Eevised 
Edition.  In  great  part  Eevvritten,  Rearranged,  and  with  many  new 
and  important  Illustrations.  Edited  by  P.  H.  Austen,  M.D.,  Professor 
of  Dental  Science  and  Meclianism  in  the  Baltimore  College  of  Dental 
Surgery.     With  nearly  400  Illustrations.     Royal  octavo. 

Price,  in  cloth,  6.50 ;  in  leather,  7.50 

HARRIS  (CHAPIN  A.),  M.D.,  D.D.S. 

A  Dictionary  of  Medical  Terminology,  Dental  Sur- 
gery, and  the  Collateral  Sciences.  Fourth  Edition, 
Carefully  Revised  and  Enlarged.  By  Ferdinand  J.  S.  Gorgas,  M.D., 
D.D.S.,  Professor  of  Dental  Surgery  in  the  Baltimore  College,  etc. 
Royal  octavo.  Price,  in  cloth,  6.50 ;  in  leather,  7.50 

RICHARDSON  (JOSEPH),  D.D.S. 

A  Practical  Treatise  on  Mechanical  Dentistry.  Third 
Edition,    much   Enlarged.     With  185   Illustrations.     Octavo. 

Price,  in  cloth, 4.00;  in  leather,  4.75 

TAFT  (JONATHAN),  D.D.S. 

A  Practical  Treatise  on  Operative  Dentistry.  Third 
Edition,  thoroughly  Revised,  with  Additions.  Over  100  Illustrations. 
Octavo.  Price,  in  cloth,  4.25 ;  in  leather,  5.00 

WEDL  (CARL),  M.D. 

Dental  Pathology.  With  Special  Reference  to  the  Anatomy  and 
Physiology  of  the  teeth,  and  notes  by  Thos.  B.  Hitchcock,  M.D., 
Prof,  of  Dental  Pathology,  Harvard  University.     105  Illustrations. 

Price,  in  cloth,  3.50  ;  in  leather,  4.50 

HANDY  (WASHINGTON  R.),  M.D. 

Handy's  Text-Book  of  Anatomy  and  Guide  to  Dis- 
sections.    For  the  use  of  Students.    312  Illustrations.     Octavo. 

Price,  cloth,  3.00 

LEBER  AND  ROTTBNSTEIN  (Drs.) 

Dental  Caries  and  Its  Causes.  An  Investigation  into  the 
Inlluaice  of  Fungi  in  the  destruction  of  the  Teeth.  With  Illustra- 
tions. Price,  cloth,  1.25 

SEWILL  (H.  E.),  M.R.C.S.,  Eng.,  L.D.S. 

The  Student's  Guide  to  Dental  Anatomy  and  Sur- 
gery.    With  77  Illustrations.  Price,  cloth,  1.50 

SANSOM  (ARTHUR  ERNEST),  M.B. 

Chloroform.     Its  Action  and  Administration.         Price,  cloth,  1.50 

TURNBULL  (LAURENCE),  M.D. 

The  Advantages  and  Accidents  of  Artificial  Anaes- 
thesia. A  Manual  of  Ansesthetic  Agents,  Modes  of  Administration, 
etc.    Second  Edition,  Enlarged.    25  Illustrations.     Price,  cloth,  1.50 


A 


PRACTICAL   TREATISE 


MECHANICAL   DENTISTRY. 


JOSEPH  RICHARDSON,  D.D.S.,  M.D., 

PROFESSOR  OF  THE  PRIXCIPLES  OF  PROSTHETIC    DENTISTRY  K  THE    INDIANA    DENTAL 

COLLEGE;    FORMERLY    PROFESSOR  OF  MECHANICAL  DENTISTRY  AND 

METALLURGY  IN  THE  OHIO  COLLEGE  OF 

DENTAL  SURGERY. 


THIRD    EDITION, 
REVISED    AND    ENLARGED, 

WITH 

ONE  HUNDRED  AND  EIGHTY-FIVE  ILLUSTRATIONS. 


PHILADELPHIA: 

LINDSAY   &    BLAKISTON. 

18  80. 


Entered  according  to  Act  of  Congress,  in  the  year  1880, 

By  LINDSAY  &  BLAKISTON, 

lu  the  Office  of  the  Librarian  of  Congress,  at  Washington,  D.  C. 


€n 


JAMES  TAYLOR,  M.D.,  D.D.S., 

KMEBITUS  PEOFESSOR  OF  THE  INSTITUTES  OF  DENTAL  SCIENCE  IN  THE  OHIO 
COLLEGE  OF  DENTAL  SURGERY, 


ACKNOWLEDGMENT  OF  PROFESSIONAL  EMINENCE 
AND  PRIVATE  WORTH, 


€^u  Mmu  is  grntrfnllt[  instrih^^; 


HIS  FEIEND  AND  FORMER  PUPIL, 

THE  AUTHOR. 


PREFACE  TO  THIRD  EDITION. 


In  responding  to  the  demand  made  for  a  third  edition  of 
the  presf  nt  work,  the  author  has  subjected  the  preceding  one 
to  a  careful  and  thorough  revision,  and  has  endeavored  to 
make  it,  as  nearly  as  practicable,  a  faithful  reflex  of  the  ad- 
vanced thought  and  experience  of  the  profession  in  all  essen- 
tial matters  relating  to  the  facts,  appliances,  methods,  and 
principles  appertaining  to  the  department  of  prosthetic  dent- 
istry. 

In  this  endeavor  no  attempt  has  been  made  to  incorporate 
the  almost  limitless  shades  of  opinion  which  prevail  among 
members  of  the  profession  concerning  methods  and  appliances, 
or  the  almost  equal  diversity  of  the  latter  themselves.  Much, 
therefore,  of  individual  thought,  experience,  and  modes  of 
operating,  differing  chiefly  in  the  manipulative  details  by 
which  similar  objects  and  results  are  sought  to  be  obtained  by 
different  practitioners,  are  necessarily  excluded.  While  there 
are  undoubtedly  many  appliances  and  methods  of  procedure 
which  are  approved  and  meritorious,  the  limits  of  the  work 
can  admit  only  those  which,  in  the  judgment  of  the  author, 
are  esteemed  typical  of  the  best. 

In  addition  to  the  consideration  of  new  and  improved  meth- 
ods and  ai)pliances  of  more  recent  introduction,  as  well,  also, 
as  conspicuous  supplementary  matters  in  connection  with  the 
older  on(!S,  the  reader  will  find  throughout  the  body  of  the 
present  work  not  only  interpolations  of  important  facts  relat- 
ing to  the  minor  details  of  practice,  but  also  careful  elimination 
of  Biicli  ])ortions  of  the  original  text  as  are  believed,  on  more 
matured  reflection,  to  be  at  variance  with  accepted  facts  and 


Vlll  PEEFACE. 

theories.  This  is  done  under  the  conviction  that  it  is  the 
province  of  a  work  like  the  present  to  preserve  and  perpetu- 
ate only  that  which  survives  the  ordeal  of  experience,  and  to 
teach  only  that  which  has  the  sanction  and  approval  of  the  en- 
lightened judgment  of  the  profession. 

As  still  occupying  somewhat  middle  ground  between  con- 
demnation and  approval,  the  chapter  on  Vulcanite  Base,  with 
some  modifications,  has  been  retained  in  deference  to  many 
who  continue  to  claim  for  it  important  advantages  as  a  cheap 
and  convenient  base.  The  growing  distrust  of  its  fitness,  how- 
ever, for  this  purpose,  points  to .  the  conclusion  that,  at  no 
distant  day,  it  will  be  classified  among  the  obsolete  processes. 

While  the  reader  will  share  the  author's  regret  that  nothing 
additional  appears  from  the  pen  of  Dr.  John  Allen  in  connec- 
tion with  the  subject  of  Continuous  Gum  Work,  by  reason  of 
afflictive  surroundings  which  rendered  it  impossible  for  him  to 
farther  enrich  this  chapter  with  the  results  of  his  added  ex- 
perience, yet,  with  the  additional  practical  details  relating  to 
this  unequalled  process  obtained  from  other  sources,  it  is  be- 
lieved the  descriptions  found  embodied  in  the  present  volume 
are  exceptionally  full  and  complete. 

An  additional  chapter  relating  to  Celluloid  as  a  base  has  been 
introduced,  embracing  a  full  and  particular  account  of  the  most 
approved  appliances  and  methods  of  manipulating  this  ma- 
terial. 

A  new  chapter  is  also  introduced  relating  to  an  approved 
method  of  recent  introduction  entitled  "  Gold  Alloy  Cast 
Base,"  of  which  Dr.  Reese,  of  Brooklyn,  N.  Y.,  is  the  inven- 
tor, and  to  whom  the  author  is  indebted  for  detailed  descrip- 
tions and  illustrative  models. 

A  distinct  chapter  has  also  been  assigned  to  the  subject  of 
Porcelain  Teeth  in  connection  with  Carved  Block-work,  em- 
bracing an  interesting  account  of  their  composition  and  manu- 
facture, with  reflections  upon  the  aesthetic  requirements  of 
prosthetic  practice. 

A  separate  chapter  has  also  been  given  to  an  account  of  the 
method  of  attaching  teeth  to  a  metallic  plate  base  by  means  of 


PREFACE.  IX 

rubber  or  celluloid,  a  process  of  constructing  dentures  scarcely- 
inferior  to  that  of  continuous  gum  work  itself. 

The  author  would  especially  direct  attention  to  the  chapter 
on  Pivoting  Artificial  Crowns.  The  conceded  importance  and 
superior  excellence  of  this  method  of  substitution  will  fully 
justify,  it  is  believed,  the  large  space  devoted  to  its  considera- 
tion. To  the  members  of  the  profession  whose  names  appear 
in  connection  with  the  several  methods,  the  author  is  under 
peculiar  obligations  for  personal  courtesies  and  indispensable 
aid  in  the  preparation  of  descriptive  material  and  accompany- 
ing illustrations. 

While  much  valuable  matter  has  thus  been  added  to  the 
present  volume,  the  author  has  not  hesitated  to  exclude  what- 
ever, in  his  judgment,  the  common  experience  of  the  profession 
has  demonstrated  to  be  impracticable,  and  therefore  useless. 
Among  the  omitted  matter  is  the  consideration  of  cast  alumi- 
num plate  base  and  other  forms  of  this  metal  requiring  the  use 
of  solder  as  a  uniting  medium  for  the  attachment  of  teeth. 
Long-continued,  patient,  and  intelligent  experimentation  with 
this  metal  as  a  base  has  demonstrated  its  practical  inutility, 
its  only  exceptional  use  as  such  being  confined  to  the  process 
in  which  the  attachment  is  secured  in  the  manner  described 
in  Chapter  XVI. 

For  fuller  information  on  the  subject  treated  of  in  the  con- 
cluding chapter,  and  which  could  not  be  extended  consistently 
with  the  proper  limits  of  a  work  like  the  present,  the  reader  is 
referred  to  a  recently  publislied  treatise  by  Professor  Norman 
W.  Kingsley,  entitled  Oral  Deformities,  a  comprehensive  work, 
embracing,  among  other  important  matters,  an  exhaustive  con- 
sideration of  Palatal  Defects  and  their  Treatment.  The  au- 
thor would  commend  this  invaluable  work  as  the  embodied 
thought  and  experience  of  the  foremost  and  most  successful 
practitioner  in  this  department  of  prosthetic  dental  surgery  in 
this  country  or  elsewhere ;  a  work  which  not  only  enriches,  in 
an  eminent  degree,  the  special  literature  of  the  dental  profes- 
sion, but  adds  fame  and  lustre  to  American  authorship. 

In  closing,  the  author  desires  to  express  his  sense  of  obliga- 


X  PREFACE. 

tion  to  those  members  of  the  profession  who  have  freely  and 
generously  assisted  in  placing  their  special  methods  of  operat- 
ing before  the  profession  through  the  medium  of  this  work, 
and  also  to  the  representatives  of  the  late  Dr.  S.  S.  White,  the 
members  of  the  Celluloid  and  Buffalo  Dental  Manufacturing 
Companies,  and  others,  for  needful  illustrations  and  essential 
information  respecting  appliances,  etc.  ,, 

Remembering  gratefully  the  many  valuable  suggestions 
received  .during  a  somewhat  extended  correspondence  with 
representative  members  of  the  profession,  and  cordially  appre- 
ciating the  many  substantial  and  essential  favors  voluntarily 
proffered  by  individual  practitioners,  the  author,  in  conclusion, 
trusts  that  the  present  volume,  thus  enhanced  in  value  by  the 
friendly  and  helpful  assistance  of  others,  will  continue  to  merit 
the  same  consideration  and  approval  that  have  been  accorded 
to  former  editions. 

Teree  Haute,  Ind.,  September,  18S0. 


PREFACE  TO  FIRST  EDITION. 


In  the  preparatioD  of  the  following  treatise,  the  author  has 
endeavored  to  present,  in  as  concise  and  methodical  a  form  as 
possible,  the  material  facts  and  principles  which  relate  to  the 
Mechanical  Department  of  Dental  Practice  in  its  present  ad- 
vanced condition.  In  the  accomplishment  of  this  undertaking, 
the  primary  and  leading  purpose  has  been  to  furnish  the  stu- 
dent and  more  inexperienced  practitioner  with  a  practical  guide 
to  the  manipulations  of  the  laboratory,  with  accompanying 
elucidations  of  the  elementary  principles  which  underlie  the 
practice  of  this  important  specialty.  In  furtherance  of  this 
design,  all  matters,  discussions,  and  commentaries,  not  strictly 
material,  have  been  carefully  excluded. 

The  arrangement  and  treatment  of  the  various  subjects  em- 
braced are  such,  it  is  believed,  as  will  best  facilitate  the  student 
in  the  acquisition  of  a  knowledge  of  the  department  alluded 
to,  and  the  practitioner  in  the  intelligent  and  successful  con- 
duction of  the  manipulations  which  appertain  to  this  branch  of 
Practical  Dentistry. 

In  the  belief  that  these  objects  have  been  mainly  accom- 
plished, the  work  is  respectfully  submitted  to  the  profession. 

J.  Richardson. 

Cincinnati. 


CONTENTS. 


PAGE 

Dedication, 5 

Preface, 7 


PAKT    FIKST. 

METALS  EMPLOYED   IN  DENTAL  LABORATORY  OPERATIONS,  WITH  PRE- 
LIMINARY OBSERVATIONS  ON  THE  DIFFERENT   MODES  OF 
APPLYING  HEAT. 


•  CHAPTER  I. 

DiFFEREXT  Modes  of  Applying  Heat, 17-40 

Blowpipes 17 

Mouth  Blowpipe, 18 

Bellows  Blowpipe 22 

Lamps 26 

Oil  Lamp 26 

Spirit  Lamp, 27 

Furnaces, 28 

Draft  or  Wind  Furnace, 28 

Baking  Furnace 29 

Gas  Furnace  without  Blast, .        .       • 31 

Blast  Furnace, 32 

Fuel 35 

Supports 38 

Crucibles, 40 


CHAPTER  11. 

Gold, 41-47 

Geological  Situations 41 

Geographical  Distribution, 42 

Properties  of  Gold, 42 

Influence  of  Alloying  on  the  Properties  of  Gold, 43 

ProperticH  of  Particular  Alloys  of  Gold 45 


XIV  CONTENTS. 

CHAPTEE  III. 

PAGE 

Repining  Gold,  . 48-53 

EJements  Employed, 48 

Separation  of  Foreign  Metals  from  Gold 49 


CHAPTEE  IV. 

Alloys  of  Gold  for  Dental  Purposes 54-67 

Reducing  Metals, 54 

Required  fineness  of  Gold  Plate,- 54 

Formulas  for  Gold  Plate  used  as  a  Base  for  Artificial  Dentures,  ....  55 

Formulas  for  Gold  Plate  used  for  Clasps,  Wire,  Stays,  Metallic  Pivots,  etc.,       .  57 

Gold  Solders 57 

Method  of  reducing  Gold  to  a  Lower  or  Higher  Standard  of  Fineness,  and  of 

Determining  the  Carat  of  any  given  Alloy, 59 

Table  of  Gold  Coinage  of  Difi'erent  Nations 63 


CHAPTEE  V. 

Method  of  Converting  Gold  Alloys  into  the  Required  Forms  for  Dental 

Purposes 68-75 

Manner  of  Procuring  an  Ingot, 68 

Forging, ' 70 

Laminating  or  Rolling, '.        .  70 

Thickness  of  Gold  Plate  required  as  a  Base  for  Artificial  Dentures,   ...  72 

Thickness  of  Plate  for  Clasps,  Stays,  etc., 73 

Reduction  of  Gold  Solders  into  Proper  Forms  for  Use, 73 

Method  of  obtaining  Gold  Wire, 73 

Method  of  constructing  Spiral  Springs 74 


CHAPTEE  VI. 

Silver, 76-78 

General  Properties  of  Silver, 76 

Alloys  of  Silver 76 

Reduction  of  Silver  to  the  required  forms  for  Dental  Purposes,  ....       77 
Formulas  for  Silver  Solders, 78 


CHAPTEE  VII. 

Platinum  and  the  Platinoid  Metals 79-82 

Alloys  of  Platinum, 81 

Platinoid  Metals, .       81 


CHAPTEE  VIII. 

Aluminum, 83-86 

General  Properties  of  Aluminum, •       .       83 

Alloys, ■    .       85 


CONTENTS.  XV 

CHAPTER  IX. 

PAGE 

Copper,  Zinc,  Lead,  Tin,  Aktimoxy,  and  Bismuth, 87-92 

Copper, 87 

Alloys  of  Copper, 87 

Zinc, 88 

Lead, 89 

Alloys  of  Lead, 89 

Tin, 90 

Antimony, 91 

Bismuth 91 

CHAPTER  X. 

General  Propertiesof  Alloys,  and  their  Treatment  and  Behavior  in  the 

Process  of  Compounding 93-96 


PART    SECOND. 

ARTIFICIAL  DEKTURES. 

CHAPTER  I. 

Treatment  of  the  Mouth  Preparatory  to  the  Insertion  of  Artificial 

Dentures, 97-104 

Useless  and  Diseased  Remains  of  Teeth 98 

Removal  of  Salivary  Calculus  or  Tartar, 101 

Diseased  Conditions  of  the  Mucous  Membrane  and  Gums,        ....  102 

Caries  or  Decay  of  the  Remaiuing  Teeth, 102 

Surgical  Treatment  of  the  Mouth  after  the  Extraction  of  Teeth,    .        .        .  102 
Time  Necessary  to  Elapse  after  the  Extraction  of  Teeth  before  Inserting 

Artificial  Dentures, 103 

CHAPTER  11. 

Materials  and  Methods  Employed  in  Obtaininu  Impressions  of   the 

Mouth 105-1'20 

Wax, 105 

Manner  of  Obtaining  an  Impression  of  the  Mouth  in  Wax  for  Partial 

Upper  Dentures, 106 

Manner  of  Obtaining  an   Impression  of  tlie  Lower  Jaw  in  Wax  for  Partial 

Dentures, 109 

Manner  of   Obtaining  an   Impression   of   the  Mouth  in   Wax    for  Entire 

Upper  Dentures, 110 

Manner  of  Obtaitiing  an    Impression  of  the  Lower  Jaw  in  Wax   for  Entire 

I^entures, 112 

Gutta-percha, 112 

Plaster  of  Paris, 113 

Manner  of  Obtaining  an    Impression   of  the  Mouth  in   Plaster   for  Partial 

Upper  Dentures, 115 

Manner  of  Obtaining  an  Impression  of  the   Mouth  in   Plaster  for  Entire 

Upper  Dentures 118 

Manner  of  Obtaining  an  Impression  of  the  Mouth  in  Plaster  for  ICutire  Lower 

Dentures 120 


XVI  CONTENTS. 


CHAPTER  III. 

PAGK 

Plaster  Models, 121-127 

Manner  of  Obtaining  a  Plaster  Model  from  an  Impression  in  Wax  for  Par- 
tial Dentures, 121 

Manner  of  Obtaining  a  Plaster  Model  from  an  Impression  in  Wax  for  En- 
tire Dentures, 123 

Manner  of  Obtaining  a  Plaster  Model  from  an  Impression  in  Plaster  for 
Partial  Dentures, 125 

Manner  of  Obtaining  a  Plaster  Model  from  an  Impression  in  Plaster  for  En- 
tire Dentures, 127 


CHAPTER  IV. 

Metallic  Dies  and  Counter-dies, 128-144 

Manner  of  Obtaining  a  Metallic  Die, 128 

Moulding, 128 

Dipping,       .    „ 134 

Counter-die, 135 

Essential  Properties  of  a  Die, 136 

Table  of  Fusible  Alloys, 143 


CHAPTER  V. 

Partial  Dentures 145-199 

Means  Employed  in  Retaining  Partial  Sets  of  Teeth  in  the  Mouth,       .       .  145 

Pivoting  Artificial  Crowns 145 

Circumstances  Modifying  the  Success  of  the  Operation, 146 

The  Condition  of  the  Roots,  etc.,      . 146 

Diathesis  of  the  Patient, 147 

Manner  of  Performing  the  Operation, 147 

Preparation  of  the  Root 147 

Fitting  the  Crown, 151 

Attaching  Crowns  with  Wood  Pivots, 152 

Pivots  of  Metal  and  Wood, 155 

Pivot  Plate, 158 

Dr.  E.  T.  Darby's  Method, 159 

Dr.  M.  H.  Webb's  Method, 161 ' 

Gold  Crown  faced  with  Porcelain, 164 

Dr.  M.  H.  Webb's  Method .164 

Attaching  Porcelain  Crowns  with  Steel  Screws, 166 

Dr.  E.  W.  Foster's  Method, 166 

Substituting  an  All-porcelain  Crown  upon  any  Root  in  either  Denture,        .  172 

Dr.  Bonwill's  Method, 172 

Dr.  Richmond's  Method  of  Attaching  Artificial  Crowns, 185 

Dr.  M.  H.  Chappell's  Method 187 

Substitution  of  an  Artificial  Crown  by  Pivoting  in  the  Absence  of  the  Nat- 
ural Root, 189 

Dr.  M..H.  Webb's  Method, 189 

Dr.  E.  T.  Darby's  Method, ,       .       .       .  197 


205 
209 


CONTENTS.  XVll 

CHAPTER  VI. 

PAGE 

Partial  Dentures  Retained  in  the  Mouth  by  means  of  Clasps  attached 

TO  THE  Natural  Teeth 200-220 

Eeinarks  on  the  Use  of  Clasps 200 

The  Teeth  to  which  it  is  Most  Proper  to  Attach  Clasps, 202 

Separation  of  the  Teeth,  by  Filing,  for  the  Reception  of  Clasps,      ...  204 

Modifications  in  the  Form  of  Clasps 

Modifications  in  the  Form  of  Plates  for  Partial  Dentures  Supported  in  the 

Mouth  by  Clasps, 

Swaging  or  Stamping  the  Plate 214 

Uniting  the  Plate  and  Clasps, ^^^ 


CHAPTER  VII. 

Partial  Dentures  Supported  in  the  Mouth  by  means  of  Cylinders  of 

Wood  attached  to  Tubed  Plates, 221-223 


CHAPTER  VIII. 

Partial  Dentures  Supported  in  the  Mouth  by  Pivoting  the  Plate  to 

THE  Roots  of  the  Natural  Teeth, 224-226 


CHAPTER  IX. 

Partial  Dentures  Supported  in  the  Mouth  by  Atmospheric  Pressure,    .  227-230 

Modifications  in  the  Form  of  the  Base, 227 

Manner  of  Forming  an  Air-chamber 229 


CHAPTER  X. 

Method  OF  Obtaining  an  Antagonizing  Model  for  Partial  Dentures; 
Selecting,  Arranging,  and  Antagonizing  the  Teeth;  Investing, 
Adjusting  Stays,  Soldering,  Etc. 231-245 


CHAPTER  XI. 

Entire  Dentures 246-275 

Method  of  Constructing  a  Plate  Base  for  an  Entire  Denture  for  the  Upper 

Jaw 246 

.  Mfxlifications  in  the  Form  of  Plates  for  Entire  Upper  Dentures,    ...         249 
Method  of  Constructing  a  Plate  Base  for  an  Entire  Denture  for  the  Under 


Jaw,  , 


253 


Antagonizing  Model  for  an  Entire  Upper  and  Lower  Denture,        .        .        .  255 
Antagonizing  Model  for  an  Entire  Upper  Denture  with  the  Natural  Teeth 

of  the  Ixjwer  Jaw  Ri-maiiiiiig, 258 

Dr.  Bonwill's  Anatomical  Articulator 260 

Selecting,  Arranging,  and  Antagonizing  the  Teeth  ;  Rimming  the  Plate;  At- 
taching Spiral  .Springs  ;  Investing,  Ivining,  Soldering,  and  Finishing,        .  265 


XVlll  CONTENTS. 


CHAPTER  XII. 

PAGE 

Porcelain  Teeth, 27G-306 

Components  of  Dental  Porcelain, 277 

Manufacture  of  Porcelain  Teeth 279 

Comments  on  the  iEsthetic  Requirements  of  Prosthetic  Practice,  .        .        .  282 

Carved  Block-Teeth, 285 

Composition  and  Preparation  of  the  Body, 285 

Composition  and  Preparation  of  Crown  Enamels,       ..,..,  287 

Composition  and  Preparation  of  Gum  Enamels, 288 

Antagonizing  Model  for  an  Entire  Upper  and  Lower  Denture,         .       .       .  292 

Antagonizing  Model  for  an  Entire  Upper  Denture, 292 

Forming  a  Matrix  for  Moulding  the  Body  preparatory  to  Carving  the 

Teeth, 294 

Moulding  the  Porcelain  Paste  preparatory  to  Carving  the  Teeth,   .       .        .  296 

Carving  the  Teeth, 298 

Crucing,  or  Bisciiiting, 298 

Application  of  the  Crown  and  Gum  Enamels, 300 

Final  Bating, 301 

Fitting  and  Attaching  the  Blocks  to  the  Metallic  Base 301 

Dr.  Calvert's  Method, 303 


CHAPTER  XIII. 

Uniting  Single  Porcelain  Teeth  to  Each  Other  and  to  a  Metallic  Base 
WITH  A  Fusible  Silicious  Compound,  Forming  a  Continuous  Artifi- 
cial Gum, 307-335 

Introductory  Remarks 307 

Dr.  Allen's  Methods, •  .       .        .        .  311 

Dr.  Hunter's  Formulas  and  Methods, 318 

Dr.  Haskell's  Methods, 325 

Dr.  Field's  Methods, 330 

Application  of  Continuous  Gum  to  Partial  Sets, 333 


CHAPTER  XIV. 

Vulcanite  Base,     . 336-376 

General  Properties  of  India-rubber, 336 

Compounding  Rubber  for  Dental  Purposes, 338 

Method  of  Constructing  an  Entire  Denture  in  a  Base  of  Rubber,     .       .        .  338 

Arranging  the  Teeth, 339 

Formation  of  the  Mould  or  Matrix, 342 

Packing  the  Mould, 347 

Vulcanizing, 354 

Finishing 367 

Partial  Dentures  constructed  in  a  Base  of  Rubber, 368 

Metallic  Clasps  attached  to  Rubber  Plates, 369 

Substitution  of  Plate  for  Rubber  Teeth 370 

Repairing 371 

Reiitting  Gold  or  Rubber  Plates  with  Rubber  Lining 372 

Manner  of  Obtaining  an  Exact  Duplicate  of  a  Set  of  Teeth  on  Rubber, .        .374 


CONTENTS.  xix 
CHAPTER  XV. 

PAGE 

Celluloid  Base, 377-399 

Introductory  Remarks 377 

Composition  and  Manufacture, 378 

Processes  Preliminary  to  Moulding, 380 

Selection  and  Preparation  of  the  Celluloid  Blank, 384 

Moulding, 386 

Hot  Moist  Air  (so-called  "Dry  Heat  ")  Machines, 387 

Moulding  in  Glycerin, 39O 

Moulding  in  Steam, 392 

Repairing 396 

Finishing, 399 


CHAPTER  XVI. 

Attaching  Porcelain  Teeth  to  a  Metallic  Base  with  Rubber  or  Cellu- 
loid   400-406 


CHAPTER  XVII. 

Gold  Alloy  Cast  Base, 407-415 

CHAPTER  XVIII. 

Defects  op  the  Palatal  Organs  and  their  Treatment  by  Artificial 

Means 416-438 

Dr.  Kingsley's  Artificial  Velum  and  Palate 416 

Palatine  Defects, 416 

Obturators, 417 

Artificial  Palates 420 

Artificial  Palates  for  Congenital  Fissure, 426 

Method  of  Making  an  Artificial  Palate 429 


MECHANICAL  DENTISTRY. 


PART  FIRST. 


METALS  EMPLOYED  IX  DENTAL  LABOKATORY  OPERATIONS, 
WITH  PRELIMINARY  OBSERVATIONS  ON  THE  DIF- 
FERENT MODES  OF  APPLYING  HEAT. 


CHAPTER  I. 

Different  Modes  of  Applying  Heat. 

The  application  of  heat  to  the  various  mechanical  processes 
of  the  dental  laboratory  would  seem  to  require  a  brief  descrip- 
tion of  some  of  the  agencies  employed  for  the  purpose.  As 
full  a  description  of  the  appliances  used  will  be  introduced  as 
is  compatible  with  the  scope  of  the  present  work. 

BLOWPIPES. 

Various  modifications  in  the  form  of  the  blowpipe  have 
been  introduced  from  time  to  time,  and  are  named  according 
to  the  means  used  to  produce  the  blast,  as  mouth,  bellows, 
self-OAitinr/  or  spirit,  and  hydrostatic  blowpipe. 

In  addition  to  the  varieties  mentioned,  there  are  others  used 
in  producing  extreme  degrees  of  heat,  as  the  "  oxygen  blowpipe" 
with  which  the  flame  is  blown  with  a  jet  of  oxygen ;  and 
another,  with  which  the  two  gases,  oxygen  and  hydrogen,  are 
burned,  called  the  "  oxy-hydrogen  blowpipe."     The  latter  is 

2 


18  MECHANICAL  DENTISTRY.  , 

capable  of  producing  a  heat  that  immediately  fuses  the  most 
refractory  substances^  as  quartz,  flint,  rock-crystal,  plumbago, 
etc.  With  it,  gold  is  volatilized,  and  iron  rapidly  consumed 
when  placed  in  the  flame ;  while  platinum,  next  to  iridium, 
the  most  infusible  of  all  known  metals,  has  been  melted  in 
quantities  exceeding  one  hundred  ounces  by  means  of  this 
powerful  instrument.  As,  however,  these  blowpipes  are  of  no 
special  practical  utility  in  the  dental  laboratory,  any  further 
reference  to  them  will  be  omitted.  Nor  is  it  deemed  neces- 
sary to  embrace  descriptions  of  either  spirit  or  hydrostatic 
blowpipes,  as  they  have  fallen  of  late  years  almost  wholly 
into  disuse. 

Month  Blowpipe, — This  instrument  has  been  long  in  use, 
is  simple  in  its  form  and  construction,  and,  for  general  use  in 
the  application  of  moderate  degrees  of  heat,  is  both  conve- 
nient and  economical.  Those  accustomed  to  its  use  are  enabled 
to  produce  a  continuous  blast  of  considerable  force,  and  soon 
acquire  the  facility  of  regulating  the  heat  produced  with  equal 
if  not  greater  precision  than  can  be  readily  attained  in  any 
other  way. 

The  most  simple  form  of  the  mouth  blowpipe  is  shown  in 
Fig.  1.     It  consists  usually  of  a  plain  tube  of  brass,  larger  at 

Fig.  1. 


the  end  applied  to  the  mouth,  and  tapering  gradually  to  a  point 
at  its  other  extremity,  the  latter  being  curved  and  tipped  at 
the  point  with  a  conical-shaped,  raised  margin,  to  protect  it 
from  the  action  of  the  flame ;  the  calibre  of  the  instrument 
terminates  here  in  a  very  small  orifice.  The  point  of  the  in- 
strument, as  well  as  that  part  of  it  received  into  the  mouth,  is 
sometimes  plated  with  a  less  oxidable  metal  than  brass,  as 
silver  or  platinum.     The  stem  is  generally  from  twelve  to 


BLOWPIPES,  19 

twentv  inches  in  length,  and  the  mouth  extremity  from  one- 
half  to  three-fourths  of  an  inch  in  diameter. 

In  operations  requiring  protracted  blowing,  a  somewhat  dif- 
ferent form  of  the  instrument  will  be  required,  owing  to  the 
accumulation  of  moisture  within  the  tube,  which,  being  forcibly 
expelled  from  the  orifice,  spirts  upon  whatever  is  being  heated 
and  interrupts  the  blast ;  also,  on  account  of  the  fatigue  which 
in  process  of  time  renders  the  muscles  of  the  mouth  and  face 
engaged  in  the  act  to  a  great  extent  powerless. 

The  difficulties  mentioned  may  be  obviated,  in  a  great  meas- 
ure, by  applying  the  form  of  blowpipe  represented  in  Fig.  2. 
To  the  mouth  extremity  is  attached  a  circular  concave  flange 
or  collar  which  receives  and  supports  the  lips.  To  the  shaft, 
near  its  curved  extremity,  is  adjusted  either  a  spherical  or 

Fig.  2. 


cylindrical  chamber  which  collects  and  retains  the  moisture  as 
it  forms  within  the  pipe.  By  allowing  that  part  of  the  tube 
connected  with  the  curved  end  to  pass  part  way  into  thecham- 
Vx;r,  a  basin  is  formed  at  the  depending  portion  of  the  latter, 
which,  by  collecting  the  fluids,  will  eifectually  prevent  them 
from  overflowing  and  passing  into  the  tube  beyond. 

Thoma.s  Fletcher,  of  Warrington,  England,  has  introduced 
modifications  in  the  construction  of  mouth  blowpipes,  which 
are  unquestionably  improvements  upon  the  simpler  forms  just 
described.*     One  form,  styled   the  hot-blast  mouth  blowpipe. 


*  The  several  appliances  embraced  in  the  above  chapter,  and  designated 
by  the  FiKnres  3,4,  5,  6,8,  9,  11,  lo,  16,  17,  18,  19,  are  such  jwrtions  of 
Flet'her's  heating  apparatus  as  are  more  especially  adapted  to  the  work  of 
the  dental  lalK)ratory,  and  are  l)elieved  to  possess  peculiar  and  unequalled 
advantages  in  the  application   of  heat  for  <lenta]    j)iirpo!5c.';.     For  the  illus- 


20 


MECHANICAL   DENTISTRY. 


is  shown  in  Fig.  3.  The  improvement  in  this  instance  con- 
sists in  coiling  the  air-tube  into  a  light  spiral  over  the  point 
of  the  jet.  This  coil  takes  up  the  heat  which  would  other- 
wise be  wasted,  and  utilizes  it  by  heating  the  air  in  its  passage. 
It  is  claimed  that  with  the  use  of  this  instrument  much  higher 
temperatures  ^re  reached  than  is  possible  with  the  ordinary- 
blowpipe,  and  that  with  the  same  amount  of  blowing  nearly 
double  the  work  is  accomplished,  while,  if  a  high  heat  is  not 


Fig.  3. 


Fig.  4. 


-°^=^iH^' 


required,  the  labor  of  blowing  is  reduced  in  proportion.  A 
similar  form  of  instrument  (Fig.  4)  is  made  with  a  hard-rubber 
mouth-piece. 

Another  form  of  mouth  blowpipe  by  the  same  inventor  is 


Fig.  5. 


exhibited  in  Fig.  5.     It  will  be  seen  to  be  wholly  unlike  any 
mouth  blowpipe  yet  devised,  and  admits  of  great  latitude  of 


trative  cuts  above  alluded  to,  the  author  is  indebted  to  the  Buffalo  Dental 
Manufacturing  Company,  sole  manufacturers  of  Fletcher's  heating  appa- 
ratus in  this  country. 


BLOWPIPES.  2X 

movements  in  the  application  of  heat.  The  form  of  the  mouth- 
piece is  especially  adapted  to  continued  blowing  without  strain 
on  the  lips,  while  the  opening  is  well  under  the  control  of  the 
tongue.  The  blowpipe  proper  is  held  as  a  pencil,  the  chamber 
collecting  condensed  moisture  and  preventing  the  passage  of 
heat  up  to  the  end.  The  instrument  can  be  readily  changed 
from  a  cold  to  a  hot-blast  blowpipe  by  substituting  the  coil  (b) 
for  the  plain  jet  or  tip. 

There  are  other  allied  forms  of  the  mouth  blowpipe,  but  as 
they  are  constructed  more  especially  for  chemical  examinations 
or  analyses,  and  as  they  possess  no  advantages  for  dental  purposes 
over  those  already  mentioned,  a  description  of  them  is  not 
deemed  necessary. 

In  the  production  of  heat  by  the  use  of  the  mouth  blow- 
pipe, either  an  oil  or  alcohol  lamp,  or  the  gas  flame  may  be  em- 
ployed, and  these  will  generally  be  found  sufficient  when  only 
moderate  degrees  of  heat  are  required.  When  gas  is  used,  the 
ordinary  gas-jet  should  be  inclosed  within  a  tube  of  copper, 
or  other  metal  not  easily  oxidized,  two  or  three  inches  in  length 
and  extending  some  distance  above  the  point  of  the  jet.  This 
tube  or  funnel  should  be  perforated  near  its  base  at  a  number 
of  points  for  the  free  admission  of  air,  which  will  insure  more 
perfect  combustion  of  the  gas,,  augment  the  heat,  and  provide 
against  carbonaceous  deposits  upon  the  substances  submitted  to 
the  action  of  the  flame. 

Mechanism  Involved  in  the  Act  of  Prodacuig  a  Continuous 
Blast  with  the  Mouth  Blovrpipe. — As  a  steady  continuous  cur- 
rent of  air  from  the  blowpipe  is  preferable  to  the  interrupted 
jet,  in  all  those  operations  where  it  is  desired  to  produce  a  stead- 
ily augmenting  heat,  the  following  remarks  explanatory  of  the 
method  of  producing  it  are  subjoined,  in  the  belief  that  they 
will  render  easier  a  process  not  always  readily  acquired. 

"  The  tongue  must  be  applied  to  the  roof  of  the  mouth,  so 
as  to  interrupt  the  communication  between  the  passage  of  the 
nostrils  and  the  mouth.  The  operator  now  fills  his  mouth 
with  air,  which  is  to  be  passed  through  the  pipe  by  compress- 
ing the  muscles  of  the  cheeks,  while  he  breathes  through  the 
nostrils,  and  uses  the  palate  as  a  valve.     When  tlie  mouth 


22  MECHANICAL    DENTISTRY. 

becomes  nearly  empty,  it  is  replenished  by  the  lungs  in  an 
instant,  while  the  tongue  is  momentarily  withdrawn  from  the 
roof  of  the  mouth.  The  stream  of  air  can  be  continued  for  a 
long  time  without  the  least  fatigue  or  injury  to  the  lungs.  The 
easier  way  for  the  student  to  accustom  himself  to  the  use  of 
the  blowpipe,  is  first  to  learn  to  fill  the  mouth  with  air,  and 
while  the  lips  are  kept  firmly  closed  to  breathe  freely  through 
the  nostrils.  Having  effected  this  much,  he  may  introduce 
the  mouth-piece  of  the  blowpipe  between  his  lips.  By  injSating 
the  cheeks,  and  breathing  through  the  nostrils,  he  will  soon 
learn  to  use  the  instrument  without  the  least  fatigue.  The  air 
is  forced  through  the  tube  against  the  flame  by  the  action  of 
the  muscles  of  the  cheeks,  while  he  continues  to  breathe  without 
interruption  through  the  nostrils.  Having  become  acquainted 
with  this  process,  it  only  requires  some  practice  to  produce  a 
steady  jet  of  flame.  A  defect  in  the  nature  of  the  combustible 
used,  as  bad  oil,  such  as  fish  oil,  or  oil  thickened  by  long  stand- 
ing or  by  dirt,  dirty  cotton-wick,  or  an  untrimmed  one,  or  a 
dirty  wickholder,  or  a  want  of  steadiness  of  the  hand  that  holds 
the  blowpipe,  will  prevent  a  steady  jet  of  flame.  But,  fre- 
quently, the  fault  lies  in  the  orifice  of  the  jet,  or  too  small  a 
hole,  or  its  partial  stoppage  by  dirt,  which  will  prevent  a  steady 
jet  of  air  and  lead  to  difficulty.  With  a  good  blowpipe,  the 
air  projects  the  entire  flame,  forming  a  horizontal,  blue  cone  of 
flame,  which  converges  to  a  point  at  about  an  inch  from  the 
wick,  with  a  larger,  longer,  and  more  luminous  flame  envelop- 
ing it,  and  terminating  at  a  point  beyond  that  of  the  blue 
flame."* 

Bellows  Bloivpipe. — There  are  many  processes  of  the  dental 
laboratory  requiring  the  application  of  a  higher  temperature 
than  is  obtainable  with  the  mouth  blowpipe.  A  more  power- 
ful and  persistent  air-blast  is  readily  produced  with  a  bellows 
or  foot  blower,  used  commonly  in  connection  with  a  burner  of 
suitable  form  attached  to  the  common  gas  pipes,  by  means  of 

*  The  Practical  Use  of  the  Blowpipe. — Anon. 


BLOWPIPES. 


23 


which  the  gas  is  furnished  with  the  oxygen  required  for  its 
combustion  in  a  state  of  intimate  mixture. 

A  simple  and  compact  form  of  bellows  or  foot  blower  is 
shown  in  Fig.  6.  The  pressure  obtainable  with  this  instru- 
ment is  continuous,  equable,  and  completely  under  the  control 


Fig.  G. 


of  the  operator,  but  the  current  may  be  greatly  increased  in 
power  after  the  rubber  disc  is  distended  until  forced  against  the 
net. 

A  contrivance,  essentially  d liferent  in  its  construction  from  the 
ordinary  bellows,  employed  to  produce  the  air-jet,  is  shown  in 
Fig.  7,  and  is  known  as  the  "Burgess  Mechanical  Blowpipe." 
When  in  use,  the  air  is  drawn  into  a  cylinder  and  condensed 
in  an  air-chamber,  ready  to  be  used  in  large  or  small  quantities, 
at  the  will  of  the  operator,  by  a  rapid  or  slow  movement  of 
the  treadle.  When  operating,  place  the  entire  foot  upon  the 
treadle,  so  that  an  easy  rocking  motion  is  obtained  ;  by  pressing 
the  toe  downwards  air  is  drawn  into  the  cylinder,  and  in  revers- 
ing the  motion  it  is  driven  into  the  air-chamber  above.  The 
pipe  outlet  is  much  smaller  than  in  the  mouth  blowpipe,  to  en- 
able a  pressure  to  be  obtained,  which  is  increased  or  diminished 
by  a  quick  or  slow  motion  of  the  treadle.  The  air-chamber 
is  easily  tilled,  and  when  so  a  constant  supply  of  pure  air  is  at 
the  control  of  the  operator. 


24 


MECHANICAL    DENTISTRY. 


The  blowpipes  used  in  connection  with  the  bellows  are  of 
various  forms.  Fig.  8  represents  one  form  of  apparatus  em- 
ployed in  the  application  of  the  air-blast  to  the  gas-flame. 

A  movable  gas-jet  attached  to  two  short  arms  of  an  ordinary 
gas-pipe  is  made  to  receive  within  it  the  blowpipe  point  con- 
nected with  the  rubber  tube,  the  air-tube  terminating  a  little 
within  the  open  mouth  of  the  gas-jet ;  it  is  thus  a  tube  within 
a  tube,  with  a  space  between  them  for  the  admission  and  pas- 


FiG.  7. 


Fig.  S. 


sage  of  gas.  The  gas,  being  admitted  by  turning  the  tap  con- 
nected with  the  gas-pipe,  is  ignited,  when  the  current  of  air 
from  the  bellows  will  strike  the  centre  of  the  flame  and  pro- 
ject it  upon  whatever  is  to  be  heated.  The  connected  portions 
of  the  air  and  gas  jets  are  so  attached  to  the  main  pipe  as  to 
admit  of  an  upward  and  downward  motion,  while  the  volume 
of  gas  and  air  is  readily  graduated  by  the  stop-cocks  attached 
to  the  air  and  gas  tubes. 


BLOAVPIPES. 


25 


A  bellows  blowpipe,  cbnstructed  on  similar  principles,  but 
admitting  of  greater  latitude  of  movements,  is  exhibited  in 
Fig.  9.  As  will  be  readily  observed, 
it  is  capable  of  being  adjusted  in  any 
desired  position.  The  jet  tube  may  be 
raised  or  lowered  to  any  height,  and 
turned  in  any  direction.  A  touch  will 
direct  the  flame  on  any  point  while  the 
blowpipe  stands  in  the  same  position 
on  the  table;  there  being  no  necessity 
tor  raising,  lowering,  or  adjusting  work 
before  it. 

A  very  convenient,  manageable,  and  effective  instrument, 
for  many  purposes  requiring  the  application  of  heat  in  the 
dental  laboratory,  is  the  hand  blowpipe  shown  in  Fig.  1 0.  It 
is  capable  of  producing  very  high  degrees  of  heat,  but  the  in- 
tensity of  the  latter  may  be  graduated  at  the  will  of  the  opera- 

FiG.  10. 


tor,  as  the  stop-cocks,  which  are  both  under  perfect  control  of 
the  thumb  of  the  hand  which  holds  the  blowpipe,  regulates  the 
supply  of  gas,  and  controls  the  volume  of  air.  The  air-jet  is 
one-eighth  inch  bore,  and  requires  a  supply  from  a  bellows. 

The  several  forms  of  bellows  blowpipes  introduced  here  are 
the  most  complete  and  efficient  yet  devised  for  dental  pur- 
poses. The  jet  may  be  elevated  or  depressed  at  will,  while 
the  force  of  the  air-current  and  the  volume  of  gas-flame  can 
as  readily  be  increased  or  diminished.  The  operator  is  thus 
enabled,  with  the  greatest  ease,  to  produce  a  heat  adapted  to 
the  most  delicate  operations,  or  to  instantly  change  it  to  a  heat 
so  intense  that  pure  gold  In  considerable  quantities  is  almost 
immediately  fused   in  the  flame.     They  are,  therefore,  well 


26 


MECHANICAL    DENTISTEY. 


adapted  to  all  operations  in  the  laboratory,  but  will  be  found 
of  special  utility  in  the  construction  of  work  requiring  pure 
gold  as  a  solder. 


LAMPS. 


The  lamps  most  commonly  used  by  dentists  in  blowpipe 
manipulations  are  oil  and  spirit  lamps. 

Oil  Lamp. — When  oil  is  burned,  the  form  of  lamp  repre- 
sented in  Fig.  11  may  be  used.     It  should  hold  from  one  to 


two  pints,  and  should  have  a  spout  one  inch  or  more  where  it 
joins  the  body  of  the  lamp,  tapering  gradually  to  three-fourths 


WICK    HOLDER    TURNED 
HAL"  A  REVOLUTION. 


of  an  inch  at  the  top.     The  spout  should  be  well  filled  with 
wick,  but  not  so  tightly  as  to  prevent  it  from  being  freely  sat- 


LAMPS. 


27 


urated.  The  best  combustible  is  pure  sweet  oil,  but  common 
lamp  or  lard  oil  is  generally  employed  and  answers  every  prac- 
tical purpose.  The  wick  should  be  kept  well  cleaned  and 
trimmed,  and  fresh  oil  should  be  substituted  whenever  that  in 
use  becomes  thickened  by  dirt  or  otherwise  deteriorated. 

A  somewhat  novel  form  of  oil  lamp  is  shown  in  Fig.  12. 
The  wick-holder  is  not  only  of  unique  design,  but  can  be  ad- 
justed to  any  desired  angle  by  simply  revolving  it  in  the  fixed 
collar.     The  wick-holder  lifts  out  for  refilling. 

Spirit  Lamp. — Alcohol  is  preferred  by  many  on  account  of 
its  greater  cleanliness,  although  it  does  not  afford  so  great 
a  heat  as  oil.  When  spirit  is  employed,  a  somewhat  different 
form  of  lamp  should  be  used.     With  one  like  that  described 

Fi(i.  13. 


for  oil,  there  is  danger  of  explosion  in  the  event  of  the  flame, 
mixed  with  air,  communicating  with  the  alcohol  contained  in 
the  lamp,  and  which  is  more  liable  to  happen  when  the  spout 
is  but  loosely  filled  with  wick.  To  provide  against  such 
ca.sualty,  it  is  not  unusual  to  pack  the  wick  too  closely,  which, 
by  obstructing  the  flow  of  alcohol  into  the  spout,  lessens  the 
heat  of  the  flame.  The  proximity  of  the  flame,  also,  to  the 
body  of  the  lamp,  produces  undue  waste  of  alcohol  by  evapo- 
ration. 

The  objections  stated  may  be  obviated  by  employing  a  lamp 
of  the  form  shown  in  Fig.  13.  With  a  lamp  like  that 
represented,  the  spirit  is  entirely  uninfluenced  by  the  heat  of 
the  flame,  while  explosion  is  rendered  impossible.  The  centre 
of  the  upright  portion  of  the  spout  is  traversed  by  a  small 


28  MECHANICAL  DENTISTRY. 

tube  extending  throughout,  and  open  at  both  ends  to  admit  of 
the  application  of  a  jet  of  air  to  the  lower  orifice,  impelling 
the  flame  from  the  centre  and  thereby  intensifying  the  heat. 
Around  this  central  tube  the  wick  is  arranged  ;  the  space  occu- 
pied by  the  latter  communicating  with  the  body  of  the  lamp 
through  the  horizontal  arm  of  the  spout. 

FURNACES. 

It  would  be  inconsistent  with  the  design  of  the  present  work 
to  introduce  a  description  of  any  forms  of  furnace  other  than 
those  of  practical  use  to  the  dentist.  Many  of  those,  used  in 
the  arts,  or  for  chemical  and  pharmaceutical  purposes,  em- 
brace almost  endless  varieties,  and  have  no  special  adaptation 
to  the  uses  required  of  them  in  the  dental  laboratory. 

Draught  or  Wind  Furnaee. — A  very  convenient,  portable 
and  economical  furnace  may  be  made  of  sheet  iron,  of  any 
desired  shape  or  dimensions,  though  usually  of  small  size,  and 
cylindrical  in  form.  A  light  grate,  or  heavy  piece  of  sheet 
iron,  perforated  with  holes  to  admit  of  the  passage  of  air, 
should  be  adjusted  near  the  bottom,  while  above  and  below  the 
grate  are  two  openings,  the  lower  one  communicating  with 
the  ash-pit,  and  the  upper  one  for  the  introduction  of  fuel  and 
substances  to  be  heated.  By  surmounting  this  simple  appa- 
ratus with  a  pipe,  or  connecting  it  with  the  flue  of  a  chimney, 
it  will  be  found  efficient  in  many  of  the  minor  operations  of 
the  shop,  as  melting  metals,  heating  pieces  preparatory  to  sol- 
dering, annealing,  etc. 

A  more  durable  and  serviceable  draught  furnace,  however, 
may  be  built  of  masonry,  a  convenient  form  of  which  is  repre- 
sented in  Fig.  14.  The  construction  of  this  stationary  fixture 
is  so  plainly  exhibited  in  the  cut  that  any  extended  description 
of  it  is  deemed  unnecessary.  The  upper  holes  represent  the 
entrance  to  the  fire-chambers,  which  are  distinct  from  each 
other ;  the  lower  ones  communicate  with  the  ash-pit,  which  is 
common  to  both  chambers.  Two  fire  apartments  are  here 
shown  ;  one  for  melting  and  refining  the  more  precious  metals, 


FURNACES. 


29 


heating  up  operations  for  soldering,  etc. ;  the  other  being  used 
exclusively  for  fusing  the  baser  metals,  as  zinc,  antimony,  lead, 


Fig.  14. 


etc.  These  furnaces  are  sometimes  constructed  with  a  single 
fire-chamber,  but  the  one  exhibited  is  in  every  way  preferable. 

Baking  Furnace. — The  chief  purposes  to  which  these  fur- 
naces are  applied  are  the  manufacture  of  porcelain  teeth,  single 
and  in  sectional  blocks,  the  preparation  of  silicious  compounds, 
and  the  construction  of  what  is  known  as  "  continuous  gum 
work."  The  most  recent  and  approved  form  of  this  furnace 
is  exhibited  in  Fig.  15. 

The  body  of  the  furnace  rests  upon  a  cast-iron  framework 
or  basement,  which  serves  the  purpose  of  an  ash-pit.  The  grate 
immediately  over  this  inclines  from  eacii  side  of  the  furnace 
toward  the  bottom  and  the  centre  of  the  ash-pit,  to  aiford  more 
ample  room  for  fuel  directly  underneath  tlie  lower  muffle. 


30 


MECHANICAL   DENTISTRY. 


The  upper  portion  or  body  of  the  furnace  is  made  of  fire-clay, 
and  contains  three  muffles  arranged  horizontally ;  the  upper 
two,  termed  "  annealing  muffles,"  are  designed  more  especially 
for  drying  substances,  partial  heating  preparatory  to  final 
baking,  and  to  receive  substances  from  the  lower  muffle  to  be 
gradually  cooled.  The  lower  or  main  muffle  is  for  general 
baking  purposes  requiring  the  employment  of  extreme  degrees 
of  heat.  Each  muffle  is  provided  with  fire-clay  slabs  or  slides, 
on  which  substances  to  be  heated  are  placed  and  introduced 

Fig.  15. 


inlT)  the  muffles ;  and  also  plugs  of  the  same  material  to  close 
the  openings  to  the  former.  Openings  are  made  on  each  side 
of  the  furnace,  intermediate  between  the  muffles,  for  the  intro- 
duction of  fuel,  and  to  afibrd  ready  access  to  the  latter  with 
tongs  or  other  implements.  These  entrances  are  also  provided 
with  plugs,  which  are  applied  during  the  process  of  heating. 
This  furnace  should  be  connected  with  a  flue  having  a  strong 
and  unobstructed  draught. 


FURNACES. 


31 


Gas  Furnace  without  Blast. — Fig.  16  represents  a  small  cru- 
cible furnace,  that  will  be  found  very  convenient  for  melting  and 
refining  the  precious  and  more  infusible  metals  employed  by 
the  dentist.  It  takes  crucibles  up  to  2i  by  2^  inches  outside, 
and  with  a  three-foot  chimney,  will  melt  copper,  gold,  silver, 
etc.,  in  about  ten  minutes,  or  cast  iron  in  thirty  minutes  from 
the  time  the  gas  is  lighted. 


Fig.  16. 


Fig.  17. 


The  construction  of  the  burner  usisl  with  this  furnace  is 
illustrated  by  the  sectional  diagram,  Fiii;.  17,  and  is  thus 
described.  "The  gas  enters  a  chamber  at  tiic  bottom  of  the 
burner  through  a  device  similar  to  a  Bun.sen  burner,  mixing 
witii  uir  as  it  enters,  and  is  burned  at  the  upper  ends  of  a 
series  of  concentric  tubes,  furnishing  air-spaces  alternately 
with  those  supplying  the  mixture  of  gas  and  air.  The  whole 
burner  is  constructed  of  iron,  and  will  be  found  better  able  to 
withstand  an  intense  heat,  more  durable  and  quicker  in  its 
operation    tlian    the   old   pattern,  with    gun-metal    tubes.     In 


32  MECHANICAL   DENTISTRY. 

case  metal  •  should  be  spilled  into  the  burner,  it  can  be  easily 
taken  apart  for  its  removal. 

"  Each  part  of  the  burner  is  lettered,  and  in  case  of  acci- 
dent, it  can  be  supplied  at  a  small  expense,  by  specifying  the 
letter  on  the  piece  desired. 

"  The  burner  in  its  present  shape  is  believed  to  be  the  most 
efficient  and  economical  yet  devised  for  furnace  purposes." 

The  following  instructions  in  the  use  of  this  furnace  should 
be  observed  : 

"  A  chimney  or  stovepipe  8  or  10  feet  high  may  be  used  as 
a  fixture,  and  the  draught  partially  stopped  with  a  damper  or 
slide  when  lower  temperatures  are  required,  the  gas  being 
turned  down  in  proportion ;  the  guide  for  the  proper  adjust- 
ment being  that  under  all  circumstances  the  flame 
MUST  JUST  cover  THE  CRUCIBLE  OR  MUFFLE,  but  not  extend 
into  the  chimney  so  as  to  make  it  red  hot.  When  the  flame 
covers  the  crucible  or  muffle  the  gas  is  doing  its  extreme 
duty  under  the  most  favorable  circumstances,  without  waste. 
Particles  of  flux  should  not  be  allowed  to  fall  on  the  fire-clay 
casing,  where  the  parts  touch  each  other ;  and  the  power  of 
the  furnace  should  not  be  urged  too  far  by  the  use  of  very 
long  chimneys,  as  there  is  danger  of  the  fusion  of  the  fire-clay 
parts  together  so  that  they  cannot  be  separated.  Fire-clay 
fittings,  as  a  rule,  cannot  be  safely  used  for  temperature  much 
exceeding  the  fusing-point  of  cast  iron.  Plumbago  fittings  and 
crucibles  must  be  heated  slowly  the  first  time  they  are  used. 
After  the  first  time  they  may  be  subjected  instantly  to  the  full 
power  of  the  furnace  without  injury." 

Blast  Furnace. — A  small,  compact,  and  convenient  crucible 
furnace  is  shown  in  Fig.  18.  Of  this  simple  but  powerful 
heating  apparatus,  which  will  be  found  especially  adapted  to 
the  necessities  of  the  dental  laboratory,  the  manufacturers* 
observe : 

Owing  to  the  discovery  by  Mr.  Fletcher  of  a  singularly 
perfect  non-conducting  furnace  casing,  we  are  enabled  to  pro- 

*  Buffalo  Dental  Manufacturing  Company. 


FURNACES. 


33 


duce  the  first  really  simple  gas  furnace  ever  constructerl.  This 
material  is  only  about  one-sixth  the  weight  of  fire-clay,  and 
has  not  one-tenth  its  conducting  power  for  heat. 

The  furnace  consists  of  a  simple  pot — for  holding  the  cruci- 
ble— with  a  lid,  and  a  blowpipe,  all  mounted  on  a  suitable 
cast-iron  base.  As  compared  with  the  ordinary  gas  furnace  it 
appears  almost  a  toy,  owing  to  its  great  simplicity. 

The  casing  holds  the  heat  so  perfectly  that  the  most  refrac- 
tor}' substances  can  be  fused  with  ease,  using  a  common  foot 
blower.  Half  a  pound  of  cast  iron  requires  from  7  to  12 
minutes  for  perfect  fusion ;  the  time  depending  on  the  gas 
supj»ly  and  pressure  of  air  from  the  blower. 


Fig.  18. 


The  power  which  can  be  obtained  is  far  beyond  what  is  re- 
quired for  most  purjjoses,  and  is  limited  only  by  the  fusibility 
of  the  crucible  and  casing. 

The  crucible  will  hold  about  ten  ounces  of  gold. 

An  ordinary  gas  supply  pipe  ^\  or  f  will  work  it  efficiently. 
It  requires  a  much  smaller  supply  of  gas  than  any  other  fur- 
nace known.  About  ten  cubic  feet  per  hour  is  sufficient  for 
most  purposes. 

Crucibles  must  not  exceed  2|  by  2  inches.  Any  common 
blowpipe  bellows  will  work  the  furnace  satisfactorily  except 
for  very  high  temperatures  (fusion  of  steel,  etc.),  for  which  a 
heavy  pressure  of  air  is  necessary. 

In  adjusting  this  furnace  for  use,  put  the  gauze  nozzle  of 
the  burner  closely  against  the  hole  in  the  side  of  the  casing, 
turn  on  the  gas  and  light  it   in  the  furnace.     Work  the  bel- 

3 


34 


MECHANICAL    DENTISTRY. 


lows  aud  then  put  the  cover  on  the  furnace.  The  air  supply 
should  be  such  that  a  flame  about  two  inches  long  will  play 
out  of  the  hole  in  the  cover,  and  it  may  be  adjusted  by  turning 
the  thumbscrew  on  the  side  of  the  burner.  The  amount  of 
air  and  gas  used  by  this  burner  is  very  small.  Care  should 
be  taken  that  the  right  proportion  of  each  should  be  used.  A 
very  light  but  steady  blast  of  air  will  give  the  best  results. 

A  modified  pattern  of  the  foregoing  furnace  (Fig.  19)  has 
been  designed,  retaining  all  the  peculiar  advantages  of  the  one 


Fig.  19. 


fecv;^t^"<~>  — - 


just  described,  but  burning  refined  petroleum  instead  of  gas 
as  fuel,  and  is  claimed  to  be  equally  as  efficient  as  the  gas 
furnace. 

The  burner  for  this  furnace  is  constructed  upon  the  prin- 
ciple of  an  atomizer ;  and  this  of  course  dispenses  with  a  wick. 
This  method  has  proved  the  most  efficient  of  any  that  has  been 
experimented  with. 

The  recent  improvements  consist  in  a  device  for  regulating 
the  supply  of  oil,  which  is  operated  by  the  milled  nut  (marked 
A)  shown  on  top  of  the  reservoir  in  the  cut,  and  the  addition 
of  an  annular  jet  of  air,  which  is  regulated  by  turning  the 
sleeve  (marked  B). 

This  burner  is  so  made  that  it  can  be  taken  apart  and 
cleansed,  in  case  there  should  be  any  obstruction  to  its  proper 
working.  Remove  the  burner  from  the  reservoir,  by  unscrew- 
ing the  small  screws ;  draw  out  the  oil  tube,  which  is  operated 
by  the  milled  nut  A,  take  off  the  sleeve  B,  and  remove  the 
inside  tube. 


FUEL.  35 

The  same  furnace  and  stand  are  used  for  either  gas  or  petro- 
leum,  the  lamp  being  fitted  for  adjustment  in  place  of  the  gas 
burner,  so  that  the  same  apparatus  can  be  furnished  for  burn- 
ing either  gas  or  refined  petroleum. 

There  is  no  doubt  that  these  furnaces  in  one  or  both  forms 
will  become  a  necessity  in  every  workshop,  as  they  fill  a  place 
intermediate  between  a  blowpipe  and  a  large  furnace — which 
has  never  yet  been  filled ;  whilst  their  strength,  cheapness, 
simplicity,  and  general  usefulness  recommend  them  to  all. 

A  very  useful  and  almost  indispensable  heating  apparatus 
in  the  dental  laboratory,  suitable  for  drying,  boiling,  melting 
metals  requiring:  a  moderate  tempera- 

,  ,  .  Fig.  20. 

ture,   as  zinc,   tin,   lead,   etc.,    heating  ^ 

flasks  preparatory  to  packing  with  rub-      ^i^fel"     vZj^ 
ber,  and  a   variety  of  other  purposes,  ■SSHHSfflSH 

is  exhibited  in  Fig.  20.  ll,.,a^JII9lliB^^^ 

The  burner,   consisting,   as  will  be       ^i^^^^«'|l 
seen,  of  a  circular  perforated  gas  tube,          '^tIi^^^'— s--[iil| ^  ,i.. 
with  a  central  air-jet,  gives  a  complete     ^^^^^^I^^^^kW 
range   of  temperature,  from  a  gentle     ^^^^far^  "-^^^s^ 
current  of  warm  air  to  a  clear  red  heat, 

and  is  so  perfectly  under  control,  that  a  common  glass  bottle 
may  be  placed  on  the  tripod  and  heated  to  any  required  tem- 
perature without  the  slightest  risk  of  fracture.  For  veiy  low 
temperatures  the  ring  must  be  lighted  through  the  opening  B. 
This  gives  a  steady  current  of  heated  air  through  the  gauze 
above.  For  boiling,  melting,  etc.,  the  light  must  be  applied 
on  the  surface  of  the  gauze,  thereby  providing  a  large  body  of 
blue  flame,  which  can  be  urged  by  the  blast-pipe  C.  This  is 
one  of  the  most  generally  useful  burners,  and  stands  hard  dirty 
work  without  injury.  The  gauze  if  choked  up  with  dirt  can 
be  replaced  in  a  few  seconds. 

FUEL. 

Under  this  head  are  comprehended  such  combustible  sub- 
stances as  are  used  for  fires  or  furnaces,  as  v)ood,  coal,  charcoal, 


36  MECHANICAL,   DENTISTRY. 

and  Gohe.  For  dental  furnace  operations  only  the  latter  two 
are,  as  a  general  thing,  admissible. 

Bituminous,  or  pit  coal,  is  unfit  for  the  uses  required  of  fuel 
by  the  dentist,  and  is  therefore  seldom  used. 

Anthracite  coal,  if  carefully  selected,  may  be  employed,  pro- 
vided it  is  clean,  free  from  slate,  and  does  not  yield  a  fusible 
ash.  As  charcoal  and  coke  are  the  fuels  chiefly  used  in  the 
processes  of  the  laboratory,  these  substances  will  be  more  par- 
ticularly described. 

Charcoal. — Charcoal  is  obtained  by  igniting  wood  and  then 
excluding  it  from  the  air  while  burning;  the  volatile  products 
are  thus  driven  off  while  the  carbon  remains.  When  com- 
bustion has  proceeded  slowly  for  a  certain  length  of  time,  the 
openings  to  the  bed  or  mound  are  closed,  and  the  wood 
allowed  to  char. 

When  it  is  desired  to  maintain  a  high  heat  in  a  small  com- 
pass, the  charcoal  best  adapted  to  the  purpose  is  that  obtained 
from  what  is  termed  hard  wood,  as  the  beech,  the  oak,  the 
alder,  the  birch,  the  elm,  etc.  A  cubic  foot  of  charcoal  derived 
from  these  woods  weighs,  upon  an  average,  from  twelve  to 
thirteen  pounds ;  while  a  similar  bulk  obtained  from  soft  wood, 
as  the  fir,  the  different  kinds  of  pine,  the  larch,  the  linden,  the 
willow,  and  the  poplar,  averages  only  from  eight  to  nine 
pounds.*  There  is,  therefore,  economy  in  the  use  of  the  for- 
mer when  purchased  by  the  bulk ;  and  of  this  class  the  beech- 
wood  charcoal  is  the  best,  on  account  of  its  greater  specific 
gravity.  The  more  heavy  charcoals  require  a  stronger  draught 
than  those  of  a  lighter  character,  as  a  more  generous  supply  of 
oxygen  is  necessary  to  their  perfect  combustion.  Charcoal 
should  be  kept  as  dry  as  practicable,  since  it  rapidly  absorbs 
moisture  from  the  atmosphere,  by  which  its  calorific  energy  is 
materially  impaired. 

Cohe. — This  substance,  like  charcoal,  is  a  carbonaceous  resi- 
duum obtained  from  pit  coal  that  has  been  exposed  to  ignition 
for  some  time,  excluded  from  the  contact  of  air,  the  volatile 

*  Ure. 


FUEL.  37 

products  of  the  coal,  like  those  of  wood,  having  been  driven 
off  bv  the  heat.  Coke  differs  in  appearance  as  well  as  in 
quality.  The  principal  part  of  that  obtained  from  gas  houses 
is  of  a  dull,  iron-black  color,  very  spongy  and  friable,  and  is 
more  rapidly  consumed,  and  produces  less  heat  than  the  harder 
and  more  compact  kinds.  The  best  coke  for  furnace  use  is 
that  used  by  brassfounders,  and  has  a  steel-gray  color,  with  a 
somewhat  metallic  lustre ;  is  compact  in  its  structure,  and  splits 
into  pieces  having  a  longitudinal  fracture. 

Coke  does  not  readily  ignite,  and  at  first  generally  requires 
the  admixture  of  charcoal  to  effect  its  combustion ;  it  also  re- 
quires a  strong  draught  to  burn  it,  but  when  thoroughly 
ignited  it  produces  an  intense  and  persistent  heat.  It  is  the 
principal  fuel  used  in  baking  mineral  teeth,  porcelain  blocks, 
and  the  silicious  compounds  employed  in  the  fabrication  of 
continuous  gum  work. 

Professor  Piggot,  in  his  remarks  on  the  comparative  value  of 
fuels,  observes:  "Practically,  for  the  purposes  of  the  chemist, 
the  best  fuel  is  charcoal  or  coke,  or  a  mixture  of  the  two.  The 
ash  of  charcoal  being  infusible  it  passes  through  the  bars  of 
the  grate  as  a  white  powder.  Should  potash,  however,  be  in 
large  exce&s  it  corrodes  the  bricks,  by  forming  with  them  a 
silicate  of  potash,  which  runs  down  the  walls  and  chokes  the 
bars.  In  small  quantities  this  action  is  beneficial,  as  it  fur- 
nishes a  protective  varnish,  and  unites  the  bricks  and  lutes, 
by  forming  a  sort  of  cement,  which  intimately  combines  with 
them. 

"  Coke  contains  a  very  variable  amount  of  ash,  which  is 
composed  chiefly  of  oxide  of  iron  and  clay.  The  latter  is  not 
fusible  by  itself,  but  may  soften.  When  pure  it  forms  a  harm- 
less slag,  which  injures  neither  the  furnace  nor  the  crucibles. 
Usually,  however,  the  oxide  of  iron  predominates.  In  this 
case  the  ash  is  very  injurious,  for  it  is  reduced  to  a  protoxide, 
which  is  not  only  fusible,  but  powerfully  corrosive  to  all 
argillaceous  matters,  so  that  both  the  crucibles  and  furnaces 
suffer."  * 


*  Dental  Chemistry  and  Metallurgy,  p.  274. 


38  MECHANICAL   DENTISTRY. 

In  order  that  the  greatest  amount  of  heat  may  be  evolved 
from  these  fuels,  it  is  necessary  that  the  conditions  necessary 
to  secure  their  perfect  ignition  should  be  strictly  observed ; 
these  have  reference  to  an  unobstructed  circulation  of  air,  that 
oxygen  may  be  freely  supplied  to  them.  To  this  end  the  fur- 
nace should  be  kept  clean,  the  bars  of  the  grate  unbroken,  and 
a  good  draught  obtained.  The  condition  in  which  the  fuel  is 
applied  will  also  modify  the  results :  thus,  for  example,  if  the 
lumps  are  too  large  they  will  absorb  heat,  and  caloric  will  be 
lost;  if  too  small  they  Avill  be  too  rapidly  consumed.  It  is 
essential,  also,  to  have  the  fuel  as  free  as  possible  from  dust  and 
dirt,  as  these  fine  particles,  in  any  considerable  quantities,  ob- 
struct the  draught,  and  prevent  a  thorough  ignition  of  the 
mass.  Coke,  especially,  should  be  preserved  clean,  and  should 
be  broken  into  fragments  not  larger  than  an  inch  or  an  inch 
and  a  half  in  diameter,  and,  as  nearly  as  possible,  in  the  form 
of  blocks  or  cubes,  as  these  leave  more  open  spaces  for  the  free 
circulation  of  the  air. 

SUPPORTS. 

There  are  many  processes  in  the  dental  laboratory  requiring 
the  application  of  heat,  for  which  a  suitable  holder  or  support 
should  be  provided.  A  very  convenient  form  of  holder,  used 
in  soldering,  may  be  made  of  a  circular  or  semi-el iptical  piece  of 
heavy  sheet  iron,  the  margin  being  serrated  and  turned  at  right 
angles,  forming  a  cup.  To  the  under  side  and  centre  of  this 
an  iron  rod,  ten  or  twelve  inches  long,  may  be  permanently 
riveted ;  or  it  may  be  made  to  revolve  on  the  handle,  so  that 
the  heat  may  be  thrown  directly  upon  any  particular  part  of 
the  piece  to  be  soldered  without  disturbing  the  latter. 

A  small  hand-furnace  (Fig.  21)  is  sometimes  used,  and  will 
be  found  a  very  convenient  and  useful  apparatus,  not  only  for 
soldering,  but  for  preparatory  heating.  It  consists  of  a  funnel- 
shaped  receptacle  made  of  sheet  iron,  with  a  light  grate  or  per- 
forated plate  of  the  same  material  adjusted  near  the  bottom, 
and  an  opening  on  one  side,  underneath  the  grate,  for  the  ad- 
mission of  air.     The  upper  part  of  the  holder  is  surmounted 


SUPPORTS. 


39 


by  a  cone-shaped  top,  whicli  may  be  readily  removed  by  a 
handle  attached  to  it ;  while  to  the  bottom  of  the  furnace  is 
attached  an  iron  rod,  five  or  six  inches  long,  and  terminating 
in  a  wooden  handle.  The  piece  to  be  soldered  is  to  be  placed 
inside  on  a  bed  of  charcoal,  the  top  adjusted  to  its  place,  and 
the  fuel  ignited ;  when  the  operation  is  sufficiently  heated  the 
top  may  be  lifted  off,  and  the  piece  remaining  in  the  furnace 


Fig.  21, 


soldered   with   the  blowpipe  in  the  usual  manner,  the  furnace 
thus  serving  the  purpose  of  a  holder. 

A  support  in  very  common  use  consists  simply  of  a  large 
close-grained  piece  of  charcoal,  invested  in  plaster  one-half  or 
three-fourths  of  an  inch  thick,  one  end  or  side  being  left  open 
and  scooped  out  to  receive  whatever  is  being  heated.  Or  a 
plaster  cup  two  or  three  inches  deep  may  be  made,  and  its 
interior  partly  filled  with  a  mixture  of  plaster,  sand,  asbestos, 
and  pulverized  cliarcf)al.  Carbon  blocks,  suitably  moulded, 
may  also  be  used.  They  are  cleanly,  perfect  non-conductors, 
and  imperishable. 


40  MECHANICAL   DENTISTRY. 


CRUCIBLES. 


Crucibles  are  small  conical -shaped  vessels  used  by  the  dent- 
ist principally  for  the  purposes  of  melting  and  refining  metals 
used  for  plates,  compounding  metallic  alloys,  preparing  and 
compounding  the  various  ingredients  employed  in  the  manu- 
facture of  porcelain  teeth  and  continuous  gum  work,  etc. 
They  combine  in  a  high  degree  the  properties  of  infusibility, 
exemption  from  the  attack  of  substances  fused  in  them,  the 
power  of  resisting  sudden  alternations  of  temperature,  and 
impermeability  to  fluids  and  gases.  The  Hessian  crucibles, 
which  are  in  most  common  use  among  dentists,  are  composed 
of  silica,  alumina,  and  oxide  of  iron.  Plumbago  crucibles  are 
also  made  from  special  patterns,  and  expressly  designed  for 
Fletcher's  furnaces.  For  a  more  particular  description  of  the 
various  components  entering  into  the  structure  of  crucibles,  as 
well  as  the  manner  of  manufacturing  them,  the  reader  is  refer- 
red to  Piggot's  Dental  Chemistry  and  Metallurgy,  and  other 
works  treating  more  fully  of  the  subject. 


GOLD.  41 


CHAPTER   11. 

Gold. 

Gold  has  been  known  from  a  period  of  great,  antiquity? 
has'ing,  according  to  the  writings  of  Moses,  been  wrought 
into  articles  of  jewelry  more  than  three  thousand  years  ago. 
As  a  base  or  support  for  artificial  dentures,  it  has  entirely 
superseded  the  use  of  the  various  animal  substances  formerly 
employed,  and,  by  the  mass  of  practitioners  at  the  present 
time,  it  continues  to  be  the  most  highly  esteemed  metal  for 
the  purpose  mentioned,  notwithstanding  the  more  recent  in- 
troduction of  approved  processes  in  which,  as  a  base,  this 
metal  is  wholly  discarded. 

Gold  is  found  only  in  the  metallic  state,  and  occurs  either 
crystallized  in  the  cube,  and  its  allied  forms,  or  in  threads  of 
various  sizes,  twisted  and  interlaced  into  a  chain  of  minute 
octahedral  crystals;  also  in  spangles  or  roundish  grains. 
Ihese  latter,  when  they  occur  of  a  certain  magnitude,  are 
called  pepitas,  some  specimens  of  which  have  been  obtained 
of  great  size.  In  1810  a  mass  of  alluvial  gold  weighing 
twenty-eight  pounds  was  found  in  the  gravel  pits  of  the 
creeks  of  Rockhole,  in  North  Carolina.  A  lump  of  gold  ore 
•weighing  three  cwt.,  was  forwarded  from  Chili,  South  Ame- 
rica, as  a  contribution  to  the  World's  Exhibition  in  London. 
New  Granada,  California,  Russia,  and  Australia,  have  each 
produced  pepitas  or  masses  of  gold  Aveighing  respectively 
twenty-seven  and  a  half,  twenty-eight,  seventy,  and  one  hun- 
dred and  six  pounds. 

Geological  Situations. — The  crystalline  primitive  rocks,  the 
compact  transition  rocks,  the  trachytic  and  trap  rocks,  and 
alluvial  grounds,  are  the  formation  in  which  gold  occurs. 
Unlike  many  other  metals,  it  is  never  in  such  large  quantities 


42  MECHANICAL   DENTISTEY, 

as  to  constitute  veins  by  itself,  but  is  either  disseminated 
through  the  rocky  masses,  or  spread  out  in  thin  plates  or 
grains  on  their  surface,  or  confined  in  their  cavities  in  the 
shape  of  filaments  or  crystallized  twigs.  The  minerals  com- 
posing the  veins  are  either  quartz,  calcspar,  or  sulphate  of 
baryta.  The  ores  associated  with  the  gold  in  these  veins  are 
principally  iron,  copper,  arsenical  pyrites,  galena,  and  blende. 
The  most  abundant  sources  of  gold,  however,  are  in  alluvial 
grounds,  where  it  is  found  distributed  in  the  form  of  spangles 
in  the  sands  of  certain  plains  and  rivers,  especially  at  their 
re-entering  angles,  at  the  season  of  low  water,  and  after 
storms  and  temporary  floods.  Sufficient  reasons  have  been 
advanced  in  sup2)ort  of  the  belief  that  gold,  found  in  alluvial 
situations,  belongs  to  the  grounds  traversed  by  these  rivers, 
instead  of  being  washed,  as  was  formerly  supposed,  from  the 
mountains  in  which  their  waters  have  their  origin. 

Geographical  Distribution.  —  The  European  mines,  more 
particularly  distinguished  for  their  richness,  are  in  Hungary 
and  Transylvania,  especially  the  former.  Gold  also  occurs, 
but  more  sparingly,  in  Ireland,  Sweden,  Siberia,  Germany, 
Russia,  and  Spain.  In  Asia  and  Africa,  the  mines  which 
yield  most  abundantly,  are  situated  in  the  southern  portions 
of  these  continents.  From  the  latter,  the  ancients  derived 
the  greater  portion  of  their  gold.  Several  of  the  South 
American  provinces  yield  this  metal  in  considerable  quanti- 
ties. Washings  are  also  common  in  several  States  of  the 
Union,  but  California  stands  unrivalled,  except  by  Australia, 
in  the  immense  productiveness  of  its  mines,  and  its  resources 
in  respect  to  this  rare  and  valuable  metal  are  reckoned  inex- 
haustible. 

Properties  of  Gold. — Pure  gold  is  distinguished  from  all 
other  metals  by  its  brilliant  orange-red  or  yellow  color,  being 
the  only  simple  metal  that  possesses  this  complexion.  It  is 
susceptible  of  a  high  polish,  but  is  inferior  in  brilliancy  to 
steel,  silver,  or  mercury.  Its  specific  gravity  varies  some- 
what, according  as  it  is  fused  or  hammered;  the  former 
having  a  density  of  19.26;  the  latter  ranging  from  19.4  to 


GOLD.  43 

19.65.     It  is  only  excelled  in  density,  therefore,  by  platinum, 
the  specific  gravity  of  which  is  21.25. 

Gold  surpasses  all  other  metals  in  malleability.  The  aver- 
age thickness  of  ordinary  gold  leaf  is  ^go'ij??^  of  an  inch,  but 
the  ultimate  degree  of  attenuation  of  which  pure  gold  is 
susceptible  exceeds  considerably  this  estimate.  It  is  also 
distinguished  for  its  ductility.  A  single  grain  of  gold  may 
be  drawn  into  wire  500  feet  in  length,  while  an  ounce  may  be 
made  to  extend  1300  miles.  It  is  somewhat  softer  than 
silver,  and  possesses  great  tenacity,  though  inferior  in  this 
quality  to  iron,  copper,  platinum,  or  silver.  A  thread  of 
gold  i-jf-Q  of  an  inch  in  diameter  will  sustain  a  weight  of  150 
pounds.  Gold  fuses  at  2016°  with  considerable  expansion, 
and,  on  cooling,  contracts  more  than  any  other  metal. 

On  account  of  the  want  of  affinity  of  gold  for  oxygen,  it 
remains  unaltered  in  the  longest  exposure ;  it  is  incapable  of 
being  oxidized  in  any  heat  that  may  be  applied  to  it,  and  is 
only  volatilized  with  great  difficulty  in  the  resistless  heat  of 
the  oxy-hydrogen  blowpipe.  It  is  unaffected  by  the  most 
concentrated  of  the  simple  acids,  but  is  readily  soluble  in 
aqua  ref/ia  or  nitro-muriatic  acid,  and  nitro-fluoric  acid. 

It  will  thus  be  seen  that  gold  possesses,  in  an  eminent 
degree,  those  general  properties  which  render  it  peculiarly 
fit  for  the  purposes  to  which  it  is  applied  in  the  practice  of 
dental  prosthesis. 

Influence  of  Alloying  on  the  Properties  of  Gold. — The 
term  al/oy  signifies  a  compound  of  any  two  or  more  metals, 
as  brass,  which  is  an  alloy  of  copper  and  zinc. 

Alloys,  in  respect  to  their  uses,  are  practically  new  metals, 
and  <lifler  in  many  important  respects,  both  in  their  chemical 
and  physical  characteristics,  from  the  constituent  metals  of 
which  they  are  composed.  A  more  particular  account  of  the 
influence  of  alloying  u[)on  the  general  properties  of  metals, 
and  their  management  and  behavior  in  the  process  of  com- 
pounding, will  be  given  under  the  head  of  alloys  of  the  baser 
metals.      As  gold  combines  readily  with  most  metals,  some  of 


44  MECHANICAL   DENTISTRY. 

the  more  prominent  conditions  which  distinguish  its  alloys 
will  be  given. 

The  malleability  of  gold  is,  strictly  speaking,  always  im- 
paired by  its  union  with  other  metals.  This  effect  is  emi- 
nently characteristic  of  certain  contaminations,  as  those  with 
arsenic,  tin,  antimony,  bismuth,  lead,  etc.;  while  with  certain 
other  metals,  as  silver,  copper  and  platinum,  unless  in  excess,  this 
property  of  gold  is  so  little  affected,  as  in  no  material  degree 
to  interfere  with  its  being  worked  into  any  desired  form  for 
dental  purposes.  The  ductility  of  gold  is  also  usually  dimin- 
ished by  its  incorporation  with  foreign  metals ;  sometimes  in 
a  remarkable  degree.  Gold  is  always  rendered  harder,  and 
its  tenacity  is  generally  increased,  by  alloying,  while  its  density 
varies  with  the  particular  metal  or  metals  with  which  it  is 
combined.  Thus,  the  alloy  of  gold  with  either  zinc,  tin, 
bismuth,  antimony  or  cobalt,  has  a  density  greater  than  that 
of  the  mean  of  its  constituents,  while  the  alloys  of  gold  having 
a  less  specific  gravity  than  the  mean  of  their  components  are 
those  with  silver,  iron,  lead,  copper,  iridium  or  nickel.  Gold 
is  ordinarily  more  fusible  when  alloyed,  the  alloy  always 
melting  at  a  less  heat  than  that  required  to  fuse  the  most 
refractory  constituent,  and  oftentimes  less  than  the  more  fusible 
component.  The  alloy  of  gold  and  platinum  furnishes  an 
example  of  the  former;  the  platinum,  which  in  its  uncom- 
bined  state  is  infusible  in  the  highest  heat  of  a  blast  furnace, 
forming  a  fusible  compound  with  gold,  the  melting-point  of 
which  is  far  below  that  of  platinum.  Gold  solder,  composed 
of  gold,  copper,  and  silver,  affords  a  familiar  illustration  of  the 
latter ;  the  alloy  melting  at  a  less  heat  than  that  required  to 
fuse  its  least  refractory  component,  silver.  Gold,  which  in  its 
pure  state  has  less  affinity  for  oxygen  than  any  other  metal,  is 
rendered  more  or  less  oxidable  when  combined  with  other 
metals. 

That  gold  alloys  tend  to  be  formed  in  definite  proportions  of 
their  constituents  would  appear  from  the  phenomenon  observed 
in  the  native  gold  of  the  auriferous  sands,  which  is  an  alloy 
with  silver  in  the  ratio  of  1  atom  of  silver,  united  to  4,  5,  6, 


GOLD.  45 

12  atoms  of  gold,  but  never  with  a  fractional  part  of  an  atom. 
The  same  circumstance  is  noticed  in  connection  with  the  amal- 
gam of  silver  and  mercury.  But  as  alloys  are  generally 
soluble  in  each  other,  the  definiteness  of  this  atomic  combina- 
tion is  obscured  and  disappears  in  most  cases. 

Propei'ties  of  Particular  Alloys  of  Gold. — The  metals  with 
which  gold  is  liable  to  be  contaminated  in  the  dental  labora- 
tory are  zinc,  tin,  lead,  antimony,  bismuth,  iron  or  steel,  mer- 
cury, and  arsenic ;  as  also  excess  of  silver,  copper,  and  platinum. 
As  several  of  these  metals  when  alloyed  with  gold,  even  in 
very  minute  quantities,  are  highly  destructive  in  their  influ- 
ence upon  those  properties  which  adaj)t  this  metal  to  the 
various  wants  of  the  mechanical  operator,  and  as  their  separa- 
tion is  often  attended  with  considerable  difficulty,  annoyance, 
and  lo&s  of  time,  it  is  practically  important  that  care  should  be 
taken  to  prevent,  as  far  as  practicable,  the  admixture  of  any 
one  or  more  of  them  with  the  gold  scrap,  filings,  or  sweepings, 
which  are  to  be  re-converted  into  proper  forms  for  use.  The 
accidental  intrusion  of  these  metals,  however,  is,  to  some 
extent,  unavoidable,  and  as  an  acquaintance  with  the  more 
prominent  characteristics  or  sensible  properties  of  the  resulting 
alloys  sometimes  furnishes  valuable  indications  in  the  selection 
of  the  proper  reagents  employed  in  their  purification,  a  de- 
scription of  individual  alloys  is  introduced. 

Tin,  antimony,  bismuth,  lead,  and  arsenic  are  peculiarly 
prominent  in  their  effects  upon  the  malleability  of  gold ; 
either  of  these  metals  in  exceedingly  minute  quantities  render- 
ing gold  intractable. 

One  part  of  antimony  with  nine  parts  of  gold,  forms  a  pale, 
brittle  alloy,  and  in  the  proportion  of  one  part  of  the  former  to 
1920  of  gold,  the  resulting  compound  is  too  brittle  to  admit  of 
successful  lamination. 

An  alloy  oi'  arsenic  with  gold  containing  ^\^  of  the  former 
is  a  gray  brittle  metal,  while  in  the  proportion  of  g,Ljj,  the 
malleability  of  the  gold  is  seriously  impaired  without  suffering 
any  change  of  color.      So  energetic  is  the  influence  of  this 


46  MECHANICAL   DENTISTRY. 

i' 

metal  on  gold  that  the  latter  is  rendered  brittle  when  sub- 
jected even  to  the  vapor  of  arsenic. 

Tin,  lead,  and  bismuth  are  somewhat  analogous  to  arsenic  in 
their  influence  upon  the  malleability  of  gold,  either  of  them,  in 
almost  inappreciable  quantities,  rendering  the  latter  metal 
unmanageable  under  the  rollers.  One  part  of  lead  or  bismuth 
to  1920  of  gold  converts  the  latter  into  an  unmalleable  metal, 
while  tin  exceeds  either  in  its  remarkable  tendency  to  render 
gold  hard  and  brittle.  Alloys  of  gold  with  tin  are  of  a  light 
color ;  those  with  lead  are  of  a  darker  complexion. 

Zine  with  gold  forms  a  brittle  alloy,  and  when  combined  in 
equal  proportions,  is  exceedingly  hard,  white,  and  brittle. 
Uniting  or  incorporating  itself  less  intimately  with  the  gold 
than  either  lead  or  tin,  however,  it  not  unfrequently  happens 
that  portions  of  the  ingot  will  be  brittle  while  others  remain, 
in  some  degree,  malleable;  so  that  the  bar,  when  rolled  out  in 
the  form  of  plate,  will  be  perforated  or  cracked  at  those  points 
where  the  zinc  preponderates,  Mdiile  remaining  portions  of  the 
plate  retain  a  moderate  degree  of  softness  and  pliability. 

The  working  properties  of  gold  are  not  sensibly  affected  by 
the  incorporation  of  very  small  quantities  of  iron,  as  an  alloy 
of  these  metals,  in  the  proportion  of  one  part  of  the  latter  to 
eleven  of  gold,  remains  malleable. 

Platinum,  in  itself  a  highly  refractory  metal,  \b.  as  before 
stated,  rendered  fusible  in  combination  with  other  metals. 
When  combined  with  gold  in  small  proportions,  the  latter  is 
rendered  harder  and  more  elastic  without  having  its  mallea- 
bility practically  impaired.  Platinum  very  readily  affects  the 
color  of  gold,  the  smallest  quantities  rendering  the  alloy  pale 
and  dull-colored. 

Silver  unites  with  gold  in  every  proportion,  and  is  the  chief 
metal  employed  in  the  reduction  of  gold  to  the  required  forms 
for  dental  uses.  It  renders  gold  more  fusible,  and  imparts  to 
it  increased  hardness  without  materially  affecting  its  mallea- 
bility. The  alloy  is  light-colored  in  proportion  to  the  amount 
of  silver  introduced. 

Copper,  like  silver,  is  usually  combined  with  gold  in  the 


GOLD.  47 

formation  of  plate,  solders,  etc.,  and  hardens  and  renders  gold 
tougher  without  practically  impairing  its  malleability.  It 
imparts  to  the  alloy  a  deeper  red  color,  and  in  the  form  of 
plate  is  capable  of  receiving  a  polish  excelling  in  richness  and 
brilliancy  any  other  metal. 

The  foregoing  alloys  of  gold,  it  will  be  perceived,  are  such 
as  result  from  the  incorporation  with  gold  of  minute  propor- 
tions of  any  one  of  the  base  metals  mentioned,  and  possess 
certain  physical  characteristics  that  indicate,  with  toleraljle 
certainty,  the  particular  alloying  component.  Thus,  for  ex- 
ample, if  the  alloy  is  light-colored  and  very  brittle,  the  pres- 
ence of  tin  may  be  suspected  ;  if  brittle  and  dull-colored,  lead 
is  indicated ;  if  grayish  or  dull-colored,  but  still  malleable, 
tough  and  elastic,  platinum  is  probably  present ;  if  unequally 
malleable,  or  brittle  in  spots,  the  presence  of  zinc  may  be 
inferred. 

Alloys  of  gold,  however,  embracing  several  or  all  of  these 
metals  in  varying  proportions,  are  sometimes  accidentally 
formed,  in  which  case  the  more  distinctive  features  which 
characterize  the  binary  compounds  are  lost  or  obscured. 


48  MECHANICAL   DENTISTEY. 


CHAPTEE   III. 

Refining  Gold. 

Elements  Employed. — The  separation  of  foreign  metals  from 
gold  by  what  is  termed  the  "  dry  method/'  or  roasting,  is 
effected  by  the  action  on  them  of  either  oxygen,  chlorine, 
or  sulphur,  converting  them  into  oxides,  chlorides,  or  sulphu- 
rets.  Certain  compound  substances  are  used  for  this  purpose 
which,  when  heated  and  decomposed,  yield  these  elements  in 
sufficient  quantities  for  the  purposes  specified.  The  refining 
agents  in  common  use  are  nitrate  of  potassa  (nitre,  or  salt- 
petre), which  yields  oxygen ;  chloride  of  mercury  (corrosive 
sublimate),  which  yields  chlorine ;  and  sidphuret  of  antimony, 
(crude  antimony),  which  yields  sulphur.  Other  compounds 
contain  these  elements,  but  those  mentioned  are  generally 
preferred,  because  iihey  contain  them  abundantly,  are  readily 
decomposed  by  heat,  and  do  not  materially  interfere  with  the 
process  of  separation  by  the  introduction  of  troublesome  com- 
ponents into  the  alloy. 

Before  considering  specifically  the  different  modes  of  refin- 
ing alloys  of  gold,  it  will  be  convenient  to  classify  the  differ- 
ent forms  of  gold  as  they  occur  in  working  this  metal  in  the 
laboratory. 

1.  Plate-scrap  or  clippings,  and  plate-filings.  These,  if 
proper  care  is  taken  to  prevent  the  introduction  of  fragments 
of  platinum,  impure  filings,  or  particles  of  base  metals,  only 
require,  provided  they  were  originally  of  suitable  fineness,  to 
be  remelted  and  again  converted  into  plate  or  other  forms 
for  use. 

2.  Mixed  filings,  and  fragments  containing  solder,  plati- 
num, etc.  These,  when  melted  alone,  produce  an  alloy  more 
or  less  impoverished  in  proportion  to  the  quantity  and  quality 


REFINING  GOLD.  49 

of  the  foreign  metals  introduced  in  finishing  pieces  constructed 
of  gold,  and  should  be  either  separately  refined  by  roasting, 
or  reduced  to  pure  gold  by  the  "  humid  method,"  to  be  de- 
scribed hereafter. 

3.  Sweepings.  This  form  embraces  many  impurities,  earthy 
and  metallic,  and  should  first  be  thoroughly  washed  to  remove 
the  earthy  constituents,  after  which  the  remaining  metals  may 
either  be  mixed  with  class  second,  or  separately  refined. 
Another,  and  perhaps  better,  method,  is  to  fuse  together  the 
sweepings  and  substances  hereinafter  mentioned,  in  the  follow- 
ing proportions :  Of  sweepings,  eight  parts;  chloride  of  sodium, 
four  parts ;  impure  carbonate  of  potassa,  four  parts ;  impure 
supertartrate  of  potassa,  one  part;  and  nitrate  potassa,  half 
part.  Mix  them  thoroughly  together,  and  melt  in  a  crucible. 
The  crucible  with  its  contents  should  remain  in  the  fire  for 
some  time,  in  order  to  secure  a  complete  separation  of  the 
metals  from  extraneous  matter. 

It  is  evident  from  the  above  classification  that  much  time 
and  labor  may  be  saved  by  preserving  these  forms  of  gold 
separately  as  they  accumulate  in  the  shop.  Separate  lapskins 
or  receptacles,  therefore,  should  be  appropriated  to  the  working 
of  gold,  one  to  receive  scrap  and  unmixed  plate-filings,  which 
may  be  re-converted  into  plate  without  refining ;  another  to 
collect  the  solder-filings,  and  such  impure  fragments  as  require 
purification. 

Sepamtion  of  Foreign  Metals  from  Gold. — The  most  trouble- 
some ingredients  which  find  their  way  into  gold  alloys  are 
what  are  commonly  called  base  metals,  as  tin,  lead,  zinc,  iron, 
antimony,  bismuth,  etc.  In  attempting  to  separate  these 
metals  from  gold,  it  is  not  a  matter  of  indifference  what  re- 
agent is  employed,  inasmuch  as  distinct  affinities  exist,  which 
may  be  advantageously  consulted.  If,  for  example,  zinc  or 
iron,  or  both  of  these  metals  are  present  in  small  quantities, 
any  compound  which  yields  oxygen  will,  by  virtue  of  the 
affinity  of  the  latter  for  these  metals,  effect  their  separation  by 
converting  them  into  oxides,  hence,  when  these  metals  arc  to 
be  got  rid  of,  nitrate  of  potassa  is  employed.     But  oxygen  has 

4 


50  MECHANICAL   DENTISTRY. 

but  a  feeble  affinity  for  tin,  and  when  this  metal  is  present,  its 
separation  is  better  effected  by  some  compound  which  parts 
with  chlorine  in  the  act  of  decomposition  ;  chloride  of  mercury 
is  therefore  used  for  the  purpose.  When  the  alloy  of  gold 
contains  a  number  of  these  metals  at  the  same  time,  and  is 
very  coarse,  sulphuret  of  antimony,  which  is  a  very  powerful 
and  efficient  reagent,  should  be  resorted  to,  unless  the  opera- 
tor should  prefer,  and  which  is  the  better  way,  to  reduce  the 
alloy  to  pure  gold  by  the  "  humid  method." 

After  all  traces  of  iron  or  steel  have  been  removed  from  the 
gold  fragments  and  filings  by  passing  a  magnet  repeatedly 
through  them,  the  latter  should  be  placed  in  a  clean  crucible, 
lined  on  the  inside  with  borax,  and  covered  either  with  a 
piece  of  fire-clay  slab,  or  broken  crucible.  Sheet-iron  has 
been  recommended  for  the  latter  purpose,  but  should  never  be 
used,  as,  when  highly  heated,  scales  form  on  the  surface,  and 
are  liable  to  drop  in  upon  the  fused  metals.  If  the  operation 
of  roasting  is  likely  to  be  protracted,  an  inverted  crucible, 
with  a  hole  in  the  bottom,  may  be  securely  luted  to  the  top  of 
the  one  containing  the  metals;  the  refining  agents  and  fluxes 
being  introduced  through  the  opening  in  the  upper  crucible. 
These  are  then  placed  in  the  furnace  on  a  bed  of  charcoal,  or 
what  is  better,  a  mixture  of  charcoal  and  coke;  the  latter 
being  built  up  around  the  crucible,  and  over  it  when  covered 
with  a  second  crucible ;  care  being  taken  that  no  fragments  of 
fuel  are  permitted  to  fall  in  upon  the  fused  metals.  Small 
portions  of  borax  may  first  be  added,  and  when  the  metals  are 
fluid,  the  refining  agents  may  be  introduced  in  small  quanti- 
ties from  time  to  time,  and  the  roasting  continued  from  half 
an  hour  to  an  hour,  according  to  the  coarseness  of  the  alloy. 
The  roasting  may  be  conducted  first  with  borax  and  nitre  to 
effect  partial  separation,  when  the  crucible  may  be  removed 
from  the  fire,  and  the  metals  allowed  to  cool  gradually.  The 
crucible  may  then  be  broken,  and  the  button  of  gold  at  the 
bottom  removed  and  separated  from  the  slag  that  covers  it 
with  a  hammer.  The  button  is  then  put  into  a  fresh  crucible 
and  re-melted.      If  there  is  any  known  base  metal  present 


REFINING    GOLD.  51' 

likely  to  render  the  gold  brittle,  the  particular  reagent  which 
will  most  readily  attack  it  may  now  be  used.  If,  however,  as 
is  generally  the  case,  the  alloy  is  of  uncertain  composition,  or 
contains  various  metals  having  distinct  affinities,  the  process 
becomes,  to  some  extent,  experimental,  and  it  may  become 
necessary  to  use  first  one  refining  agent  and  then  another, 
until  sufficient  separation  is  eiFected.  Generally,  it  will  be 
sufficient  to  use  the  nitrate  of  potassa  alone,  as  most  metals  are 
oxidable.  After  roasting  with  nitre  for  half  or  three-fourtjjs 
of  an  hour,  adding  small  portions  at  a  time,  the  melted  metals 
may  be  poured  into  ingot  moulds  previously  warmed  and 
oiled.  If,  after  hammering,  annealing,  and  rolling  the  ingot, 
it  should  still  be  found  brittle,  it  must  be  re-melted,  and  chlo- 
ride of  mercury  used  as  the  refining  agent.  This  will  remove 
any  traces  of  tin  which  may  be  present. 

If  the  alloy,  however,  is  greatly  impoverished,  it  may  be 
more  advantageously  treated  with  sulphuret  of  antimony ;  in 
which  case  the  metal  should  be  melted  in  a  large  crucible  with 
about  twice  or  three  times  their  weight  of  the  native  sulphuret, 
which  should  be  added  in  small  quantities  at  a  time.  Tlie 
heat  decomposes  the  sulphuret  of  antimony;  the  sulphur  unit- 
ing with  the  base  metals  forming  sulphurets,  and  the  antimony 
uniting  with  the  gold  forming  a  leaden-colored  alloy.  The 
antimony  may  be  parted  from  the  gold  alloy  in  the  following 
manner :  Place  the  mixture  in  a  clean  crucible,  and  when 
melted,  force  a  current  of  air  with  a  pair  of  bellows  upon  its 
surface;  this  oxidizes  the  antimony,  which  passes  off  in  the 
form  of  vapor.  The  current  should  be  mild  at  first,  as  too 
great  a  draught  is  apt  to  carry  off  portions  of  gold  by  a  too 
hurried  volatilization  of  the  antimony.  A  current  strong 
enough  to  produce  visible  fumes  will  be  sufficient.  When 
these  cease,  the  crucil)le  may  be  covered,  and  as  the  melting- 
point  of  the  gold  rises  with  the  escape  of  antimony,  the  fire 
should  be  urged  to  a  stronger  heat,  and  before  pouring,  a  for- 
cible current  of  air  should  again  ])c  thrown  upon  the  surface 
of  the  melted  metals  to  effectually  dissipate  any  remaining  por- 
tions of  the  antimony. 


62  MECHANICAL  DENTISTRY. 

If,  after  treatment  with  the  reagents  enumerated,  the  alloy 
should  be  found  malleable,  but  stiif  or  elastic,  and  dull-col- 
ored, it  is  probably  due  to  the  presence  of  platinum;  and  any 
further  attempts  to  reduce  it  by  roasting  will  prove  unavail- 
ing. It  must  then  be  subjected  to  the  process  which  will  be 
hereafter  described  for  the  separation  of  gold  and  platinum. 

When  it  is  desired  to  reduce  the  alloy  to  pure  gold,  which 
is  generally  advisable  whenever  the  gold  to  be  refined  consists 
of  very  coarse  filings,  fragments  of  plate  containing  large 
quantities  of  solder,  linings  with  platinum  pins  attached,  par- 
ticles of  base  metals,  etc.,  the  "humid  process,"  as  it  is  called, 
should  be  employed.  The  solvents  in  common  use  for  this 
purpose  are  the  nitric,  sulphuric,  and  nitro-muriatic  or  hydro- 
chloric acid ;  but  as  the  desired  results  can  be  more  conveni- 
ently and  directly  obtained  by  the  use  of  the  latter,  or  hydro- 
chloric acid,  this  most  available  method  alone  will  be  given. 
The  following  practical  remarks  on  the  process  are  copied 
from  an  article  on  the  "  Management  of  Gold,"*  by  Professor 
George  Watt. 

"  When  the  alloy  is  composed  of  metals  differing  but  little 
in  their  affinities  for  oxygen,  chlorine,  etc.,  we  resort  to  one  of 
the  '  wet  methods.'  And,  in  connection,  we  will  only  describe 
the  one  which  we  consider  the  most  convenient  and  effectual 
for  the  practical  dentist.  It  is  effectual  in  all  cases,  as  it 
always  gives  us  pure  gold. 

"  Let  us,  then,  suppose  that  our  gold  alloy  has  become  con- 
taminated with  platinum  to  such  extent  that  the  color  and 
elasticity  of  the  plate  is  objectionable.  The  alloy  should  be 
dissolved  in  nitro-muriatic  or  hydrochloric  acid,  called  aqua 
regia.  The  best  proportions  for  aqua  regia  are  three  parts  of 
hydrochloric  acid  to  one  of  nitric.  If  the  acids  are  at  all 
good,  four  ounces  of  the  aqua  regia  will  be  an  abundance  for 
an  ounce  of  the  alloy.  The  advantage  of  using  the  acids  in 
the  proportion  of  three  to  one,  instead  of  two  to  one,  as 
directed  in  most  of  the  textbooks,  is,  that  when  the  solution 
is  completed,  there  is  but  little,  if  any,  excess  of  nitric  acid. 

*  Dental  Register  of  the  West,  vol.  xii,  p.  251. 


REFINING    GOLD.  53 

If  the  acids  be  ^chemically  pure/  four  parts  of  the  hydro- 
chloric to  one  of  the  nitric,  produces  still  better  results. 

"  By  this  process  the  metals  are  all  converted  into  chlorides  ; 
and,  as  the  chloride  of  silver  is  insoluble,  and  has  a  greater 
specific  gravity  than  the  liquid,  it  is  found  as  a  grayish-white 
powder  at  the  bottom  of  the  vessel.  The  chlorides  of  the 
other  metals,  being  soluble,  remain  in  solution.  By  washing 
and  pouring  off,  allowing  the  chloride  of  silver  time  to  settle 
to  the  bottom,  .the  solution  may  be  entirely  separated  from  it. 

The  object  is  now  to  precipitate  the  gold  while  the  others 
remain  in  solution.  This  precipitation  may  be  effected  by 
any  one  of  several  different  agents,  but  we  will  mention  only 
the  protosulphate  of  iron. 

"  This  salt  is  the  common  green  copperas  of  the  shops,  and, 
as  it  is  always  cheap  and  readily  obtained,  we  need  look  no 
farther.  It  should  be  dissolved  in  clean  rain-water,  and  the 
solution  should  be  filtered,  and  allowed  to  settle  till  perfectly 
clear.  Then  it  is  to  be  added  gradually  to  the  gold  solution 
as  long  as  a  precipitate  is  found,  and  even  longer,  as  an  ex- 
cess will  the  better  insure  the  precipitation  of  all  the  gold. 
The  gold  thus  precipitated  is  a  brown  powder,  having  none  of 
the  appearances  of  gold  in  its  ordinary  state.  The  solution 
should  now  be  filtered,  or  the  gold  should  be  allowed  to  settle 
to  the  bottom,  where  it  may  be  washed  after  pouring  off  the 
solution.  It  is  better  to  filter  than  decant  in  this  case,  as, 
frequently,  particles  of  the  gold  float  on  the  surface,  and 
would  be  lost  in  the  washings  by  the  latter  process. 

"  Minute  traces  of  iron  may  adhere  to  the  gold  thus  pre- 
cipitated. These  can  be  removed  by  digesting  the  gold  in 
dilute  sulphuric  acid;  and,  when  the  process  is  properly  con- 
ducted, thus  far,  the  result  is  jyare  gold,  which  may  be  melted, 
under  carbonate  of  potash,  in  a  crucible  lined  with  borax,  and 
reduced  to  the  required  carat." 


54  MECHANICAL    DENTISTRY. 


CHAPTER  IV. 

Alloys  of  Gold  for  Dental  Purposes. 

•  Gold,  in  its  pure  state,  is  rarely  employed  by  the  dentist 
in  laboratory  processes  on  account  of  its  softness  and  flexi- 
bility; it  is,  therefore,  usually  alloyed  with  such  metals  as 
impart  to  it — without  practically  impairing  either  its  mallea- 
bility, pliancy  or  purity — the  degree  of  hardness,  strength 
and  elasticity  necessary  to  resist  the  wear  and  strain  to  which 
an  artificial  piece  constructed  from  it  is  unavoidably  exposed 
in  the  mouth.  < 

Reducing  Metals. — The  metals  with  which  gold  is  usually 
combined  are  copper  and  silver.  It  is  sometimes  reduced 
with  silver  alone,  many  regarding  the  introduction  of  copper 
into  the  alloy  as  objectionable,  as  plate  derived  from  it  is  sup- 
posed to  be  more  readily  tarnished  and  to  communicate  to  the 
mouth  a  disagreeable  metallic  taste.  This  is  unquestionably 
true,  if,  as  is  sometimes  the  case,  the  copper  used  is  in  excess ; 
when,  in  addition  to  the  effects  mentioned,  gold,  so  debased, 
may  become  a  source  of  positive  injury  to  the  organs  of  the 
mouth,  as  well  as  to  the  general  health.  The  small  propor- 
tions of  copper  usually  employed  in  forming  gold  plate,  how- 
ever, are  not  likely  to  produce,  in  any  objectionable  degree, 
the  consequences  complained  of,  unless  the  fluids  of  the  mouth 
are  greatly  perverted.  If  gold  coin  is  used  in  the  formation 
of  plate,  it  may  be  sufficient  to  add  silver  alone,  inasmuch  as 
copper  is  already  present;  though,  usually,  additional  quan- 
tities of  the  latter  metal  are  added. 

Required  Fineness  of  Gold  Plate. — Alloys  of  gold  to  be  per- 
manently worn  in  the  mouth,  should  be  of  such  purity  as 
will  most  certainly,  under  all  the  contingencies  of  health  and 
disease,  resist  any  chemical  changes  that  would  tend  to  com- 


ALLOYS  OF  GOLD  FOR  DENTAL  PURPOSES.      55 

promise  either  the  comfort  or  health  of  the  patient.  Evils  of 
no  inconsiderable  magnitude  are  sometimes  inflicted,  either 
through  ignorance,  carelessness  or  cupidity,  by  disregard  of 
this  important  requirement.  If  the  general  health  of  the  pa- 
tient remained  always  uniformly  unimpaired,  with  the  secre- 
tions of  the  mouth  in  their  normal  state,  gold  degraded  to 
eighteen  or  even  sixteen  carats  fine,  would  undergo  no  mate- 
rial changes  in  the  mouth.  But  it  must  be  remembered  that, 
in  addition  to  the  corrosive  agents  introduced  into  the  mouth 
from  without,  a  variety  of  diseases,  local  and  constitutional, 
effect  important  changes  in  the  otherwise  bland  and  innoxious 
fluids  contained  therein,  which,  from  being  alkaline  or  neutral, 
become  more  or  less  acidulated.  Indigestion,  with  acid  eruc- 
tations ;  gastro-enteritis ;  ague ;  inflammatory  and  typhoid  fe- 
vers ;  brain  affections ;  eruptive  diseases ;  rheumatism  ;  gout, 
etc.,  are  some  of  the  local  and  constitutional  disorders  almost 
uniformly  imparting  to  the  mucous  and  salivary  secretions  an 
acid  reaction.  These  readily  attack  the  impoverished  gold 
too  frequently  employed  as  a  base  for  artificial  teeth ;  and  as 
a  natural  sequence  to  such  practice  we  find  supervening,  in- 
flammation of  the  mucous  membrane  and  gums,  with  chronic 
periodontitis  and  loosening  of  the  teeth ;  aphthous  ulcers ;  gas- 
tric irritation ;  general  nervous  disorders ;  decay  of  the  teeth  ; 
foetid  breath ;  disagreeable  metallic  taste  in  the  mouth,  etc. 
Gold  plate  intended  to  be  introduced  into  the  mouth,  should 
not,  therefore,  as  a  general  thing,  be  of  a  less  standard  of  fine- 
ness than  twenty  carats.  It  may  exceed  this  degree  of  purity 
in  some  cases,  but  will  rarely  or  never,  unless  alloyed  with 
platinum,  admit  of  being  used  of  a  higher  carat  than  the  pres- 
ent American  coin,  which  is  21.6  carats  fine. 

Fonnulasfor  Gold  Plate  used  as  cr.  Base  for  Artificial  Den- 
tures.— Any  of  the  following  formulas  may  be  employed  in 
the  formation  of  gold  plate  to  be  used  as  a  base  or  support  for 
artificial  dentures.  The  relative  proportions  of  the  alloying 
components  may  be  varied  to  suit  the  peculiar  views  or  neces- 
sities of  the  manipulator.     The  estimated  carat  of  the  ap- 


56  MECHANICAL   DENTISTEY. 

pended  formulas  are  based  on  the  fineness  of  the  American 
gold  pieces  coined  in  1837  and  thereafter. 

GOLD  PLATE  EIGHTKEN   CARATS   FINE. 

Formula  No.  1.  Fm~)nula  No.  2. 

18  dwts.  pure  gold,  20  dwts.  gold  coin, 

4  dwts.  fine  copper,  2  dwts.  fine  copper, 

2  dwts.  fine  silver.  2  dwts.  fine  silver. 

GOLD  PLATE  NINETEEN   CARATS  FINE. 

Formula  No.  S.  Formula  No.  4. 

19  dwts.  pure  gold,  20  dwts.  gold  coin, 

3  dwts.  copper,  25  grs.  copper, 
2  dwts.  silver.                                    40+  grs.  silver. 

GOLD  PLATE  TWENTY   CARATS  FINE. 

Formula  No.  5.  Formula  No.  6. 

20  dwts.  pure  gold,  20  dwts.  gold  coin, 
2  dwts.  copper,  18  grs.  copper, 

2  dwts.  silver.  20+  grs.  silver. 

GOLD  PLATE  TWENTY-ONE  CARATS   FINE. 

Formula  No.  7.  Formula  No.  8. 

21  dwts.  pure  gold,  20  dwts.  gold  coin, 
2  dwts.  copper,  13+  grs.  silver. 

1  dwt.  silver. 

Formula  No.  9. 
20  dwts.  gold  coin, 

6  grs.  copper, 
7^  grs.  platinum. 

GOLD  PLATE  TWENTY-TWO  CARATS  FINE. 

Formula  No.  10. 
22  dwts.  pure  gold, 

1  dwt.  fine  copper, 
18  grs.  silver, 

6  grs.  platinum. 

The  union  of  platinum  Avith  gold,  as  in  Formula  No.  10, 
furnishes  an  alloy  rich  in  gold,  while  it  imparts  to  the  plate 
derived  from  it  a  reasonable  degree  of  stiffness  and  elasticity ; 


ALLOYS  OF  GOLD  FOR  DENTAL  PURPOSES.      57 

preserves  in  a  good  degree  the  characteristic  color  of  fine  gold  ; 
and  does  not  materially  impair  its  susceptibility  of  receiving  a 
high  polish.  The  amount  of  gold  coin  given  in  Formula 
No.  9  may  be  reduced  with  platinum  alone,  adding  to  it  from 
eight  to  twelve  grains;  in  which  case,  although  the  carat  of 
the  alloy  is  lowered,  its  absolute  purity  remains  unaffected, 
and  plate  formed  from  it  will  better  resist  any  changes  in  the 
mouth  than  gold  coin  itself. 

■  Formulas  for  Gold  Plate  used  for  Clasps,  Wire,  Stays  or 
Linings,  MetalUe  Pivots,  etc. — Gold  used  in  the  formation  of 
clasps,  stays,  etc.,  is  improved  for  these  purposes  by  the  addi- 
tion of  sufficient  platinum  to  render  it  firmer  and  more  elastic 
than  the  alloys  ordinarily  employed  in  the  formation  of  plate 
as  a  base.  The  advantages  of  this  elastic  property,  in  its 
application  to  the  purposes  under  consideration,  are,  that 
clasps  formed  from  such  alloys  will  adapt  themselves  more 
accurately  to  the  teeth,  as,  when  partially  spread  apart  on 
being  forced  over  the  crowns,  they  will  spring  together  again 
and  accurately  embrace  the  more  contracted  portions.  In  the 
form  of  stays  or  backings,  additional  strength  being  imparted, 
a  less  amount  of  substance  w'ill  be  required ;  the  elasticity  of 
these  supports,  also,  will  not  only  lessen  the  chances  of  acci- 
dent to  the  teeth  themselves  in  mastication  and  otherwise,  but 
preserve  their  proper  position  when  temporarily  disturbed  by 
any  of  the  forces  applied  to  them.  The  same  advantages  last 
mentioned  are  obtained  from  this  property  in  the  use  of  metal- 
lic pivots. 

Formula  No.  1.  Formula  No.  2. 

20  dwts.  pure  gold,  20  dwts.  coin  gold, 

2  dwts.  fine  copper,  8  grs.  fine  copper, 

1  dwt.  fine  silver,  10  grs.  silver, 

1  dwt.  platinum.  20  gi-s.  platinum. 

The  alloy  derived  from  either  of  these  formulas  will  be 
twenty  carats  fine. 

Gold  Solders. — Solders  are  a  class  of  alloys  by  means  of 
which  the  several  pieces  of  the  same  or  of  difi'erent  metals  are 


58  ,  MECHANICAL   DENTISTEY. 

united  to  each  other.  They  should  be  more  fusible  than  the 
metals  to  be  united,  and  should  consist  of  such  components  as 
possess  a  strong  affinity  for  the  substances  to  be  joined.  They 
should  also  be  as  fine  as  the  metals  to  which  they  are  applied 
will  admit  of  without  endangering  the  latter.  Solders  of 
different  degrees  of  fineness,  therefore,  should  always  be  pro- 
vided, from  which  the  one  most  suitable  for  any  given  case 
may  be  selected. 

The  use  of  solders  of  doubtful  or  unknown  composition 
should  be  avoided,  and  hence  they  should  be  compounded 
either  from  pure  gold  or  gold  coin. 

The  following  formula  taken  from  Prof.  Harris's  work  on 
Dental  Surgery,  page  664,  recipe  No.  3,  may  be  used  in  con- 
nection with  eighteen  or  twenty  carat  gold  plate,  and  is  six- 
teen carats  fine : 

6  dwts.  pure  gold, 
2  dwts.  roset  copper, 
1  dwt.  fine  silver. 

Recipes  Nos.  1  and  2,  page  663  of  same  work,  are  too 
coarse  to  be  introduced  into  the  mouth ;  the  former  being  a 
fraction  below  fourteen  carats,  while  the  latter  is  still  more 
objectionable,  exceeding  but  little,  twelve  and  one-half  carats. 

Formula  No.  1  of  the  following  recipes  is  a  fraction  over 
fifteen  carats  fine;  and  No.  2  furnishes  a  solder  eighteen 
carats  fine : 

Formula  No.  1.  Formula  No.  2. 

6  dwts.  gold  coin,  Gold  coin,  30  parts. 

30  grs.  silver,  Silver,  4      " 

20  grs.  copper,  Copper,         1      " 

10  grs.  brass.  Brass,  1      " 

■  Zinc,  as  will  be  observed  by  the  incorporation  of  brass  in 
the  above  formulas,  is  sometimes  employed,  principally  with  a 
view  of  rendering  the  alloy  more  fusible.  Its  employment 
under  any  circumstances  is  objected  to  by  many  on  the 
ground  that  it  more  readily  tarnishes  in  the  mouth,  is  more 
brittle,  and  furnishes  more  favorable  conditions  for  galvanic 


ALLOYS  OF  GOLD  FOR  DENTAL  PURPOSES.      59 

action.  These  objections  only  hold  good  when  zinc  is  nsed  in 
excess.  When  employed  in  quantities  sufficient  only  to  make 
the  gold  flow  readily  and  evenly  at  a  diminished  heat,  it  is 
claimed  that  the  base  metal  used  in  these  alloys  is  chiefly 
consumed  in  the  process  of  soldering,  leaving  a  residuum  of 
gold  equal,  or  nearly  so,  in  fineness  to  the  plate.  If  such  is 
the  case,  they  are  desirable  alloys  for  soldering  purposes,  inas- 
much as  the  importance  of  having  the  various  parts  of  a  piece 
of  dental  mechanism  differ  as  little  as  possible  in  their  affinity 
for  the  acids  of  the  mouth  is  generally  recognized. 

3Iethod  of  reducing  Gold  to  a  loivei'  or  higher  standard  of 
Fineness,  and.  of  determining  the  Carat  of  any  given  Alloy. — 
In  the  process  of  compounding  gold  for  dental  purposes,  the 
manipulator  should  always  aim  at  exactness  in  the  quantity 
and  relative  proportions  of  the  reducing  components,  and 
should  be  able  to  determine  precisely  the  purity  of  the  metals 
he  employs.  Gold  alloys  are  too  often  arbitrarily  com- 
pounded, and  used  without  any  adequate  knowleflge  of  their 
qualities  or  properties ;  and  formulas,  taken  on  trust,  are  em- 
ployed without  any  certain  knowledge  of  the  quality  of  the 
alloys  they  produce. 

That  we  may  know  certainly  the  quality  of  the  gold  alloys 
used  in  the  laboratory  without  resorting  to  the  inconvenient 
process  of  analysis  or  assaying,  they  should  always  be  made 
either  from  pure  gold  or  gold  coin,  the  standard  of  these 
being  definitely  fixed.  But  as  the  process  of  procuring  pure 
gold  is  somewhat  tedious  and  troublesome,  gold  coin  is  very 
generally  employed  for  the  purpose.  The  amount  of  alloy 
necessary  to  reduce  either  pure  or  coin  gold  to  any  particular 
standard,  whether  higher  or  lower,  and  the  method  of  ascer- 
taining the  carat  or  fineness  of  any  given  alloy,  may  be 
readily  determined  by  a  few  simple  rules.  The  following 
practical  remarks  on  the  method  are  copied  from  an  article 
on  "  Alloying  Gold,"*  by  Professor  G.  Watt. 

"  1 .  To  ascertain  the  carat  of  any  given  alloy. — The  propor- 
tion may  be  expressed  as  follows : 

*  Dental  RegiHter  of  tlie  West,  vol.  x,  p.  396. 


60  MECHANICAL   DENTISTRY. 

"  As  the  weight  of  the  alloyed  mass  is  to  the  weight  of  gold 
it  contains,  so  is  24  to  the  standard  sought.  Take,  for  exam- 
ple, Harris  No.  3  gold  solder: 

Pure  gold, 6  parts. 

"     silver, 2      " 

"     copper, '        .     1      " 

Total, 9 

"  The  proportion  would  be  expressed  thus, — 

9  :  6  :  :  24  :  16. 

"  From  this  any  one  can  deduce  the  following 

"  Rule. — Multiply  24  by  the  weight  of  gold  in  the  alloyed 
mass,  and  divide  the  product  by  the  weight  of  the  mass ;  the 
quotient  is  the  carat  sought. 

"  In  the  above  example,  24  multiplied  by  6,  the  quantity  of 
gold,  gives  144,  which,  divided  by  9,  the  weight  of  the  whole 
mass,  gives  16.  Hence,  an  alloy  prepared  as  above,  is  16 
carats  fine. 

"  As  another  example,  under  the  same  rule,  take  Harris's 
No.  1  solder. 

22  Carat  gold,  48  parts. 

silver,          .         .         .         .         .     16      " 
copper, 12      " 

Total, 76 

"  Now,  as  the  gold  used  is  but  22  carats  fine,  one-twelfth  of 
it  is  alloy.  The  one-twelfth  of  48  is  4,  which  subtracted 
from  48  leaves  44.     The  statement  then  is  : 

76  :  44  :  :  24  :  13.9. 

"  This  solder,  therefore,  falls  a  fraction  below  14  carats. 

"  2.  To  reduce  gold  to  a  required  carat. — The  proportion 
may  be  expressed  as  follows : 

"  As  the  required  carat  is  to  24,  so  is  the  weight  of  the  gold 
used  to  the  weight  of  the  alloyed  mass  when  reduced.  The 
weight  of  gold  subtracted  from  this,  gives  the  quantity  of  alloy 
to  be  added. 

"For  example,  reduce  6  ounces  of  pure  gold  to  16  carats. 


ALLOYS  OF  GOLD  FOR  DENTAL  PURPOSES.      61 

,"  The  statement  is  expressed  thus : 
16  :  24  :  :  6  :  9. 

"  Six  subtracted  from  9  leaves  3,  which  is  the  quantity  of 
alloy  to  be  added.     From  this  is  deduced  the  following 

"  Rule. — Multiply  24  by  the  weight  of  pure  gold  used, 
and  divide  the  product  by  the  required  carat.  The  quotient 
is  the  weight  of  the  mass  when  reduced,  from  which  subtract 
the  weight  of  the  gold  used,  and  the  remainder  is  the  weight 
of  alloy  to  be  added. 

"  As  another  example  under  the  same  rule,  reduce  1  penny- 
weight of  22  carat  gold  to  18  carats. 

"  As  the  gold  is  only  22  carats  fine,  one-twelfth  of  it  is 

already  alloy.     The  one  pennyweight,  therefore,  contains  but 

twenty-two  grains  of  pure  gold.     The  statement  is,  therefore, 

thus  expressed : 

18  :  24  :  :  22  :  291 

"Twenty-two  subtracted  from  29 J  leaves  7^.  Therefore, 
each  pennyweight  of  22  carat  gold  requires  7^  grains  of  alloy 
to  reduce  it  to  18  carats. 

"  3.  To  reduce  gold  from  a  lower  to  a  higher  carat. — This 
may  be  done  by  adding  pure  gold  or  a  gold  alloy  finer  than 
that  required.  The  principle  of  the  rule  may  be  set  forth  in 
the  following  general  expression  : 

"  As  the  alloy  in  the  required  carat  is  to  the  alloy  in  the 
given  carat,  so  is  the  weight  of  the  alloyed  gold  used  to  the 
weight  of  the  reduced  alloy  required.  The  principle  may  be 
practically  applied  by  the  following 

"  Rule, — Multiply  the  weight  of  the  alloyed  gold  used  by 
the  number  representing  the  proportion  of  alloy  in  the  given 
carat,  and  divide  the  product  by  that  representing  the  propor- 
tion of  alloy  in  the  required  carat;  the  quotient  is  the  weight 
of  the  mass  when  reduced  to  the  required  carat  by  adding  fine 
gold. 

"  To  illustrate  this,  take  the  following  example: 

"  Reduce  1  pennyweight  of  16  carat  gold  to  18  carats. 

"The  numbers  representing  the  proportions  of  alloy  in  this 


62  MECHANICAL    DENTISTRY. 

example  are  found  by  respectively  subtracting  18  and  16  from 
24.     The  statement  is,  therefore : 

6  :  8  :  :  1  :  li-, 

from  which  it  follows  that  to  reduce  one  pennyweight  of  16 
carat  gold  to  18  carats,  there  must  be  one-third  of  a  penny- 
weight of  pure  gold  added  to  it. 

"  But  suppose  that,  instead  of  pure  gold,  we  wish  to  eifect 
the  change  by  adding  22  carat  gold.  The  numbers,  then, 
respectively  representing  the  proportions  of  the  alloy  would 
be  found  by  subtracting,  in  the  above  example,  16  and  18  from 
22,  and  the  statement  would  be  : 

4  :  6  :  :  1  :  11. 

"  It  follows,  then,  that  to  each  j^enny  weight  of  16  carat  gold, 
a  half  pennyweight  of  22  carat  gold  must  be  added  to  bring  it 
to  18  carats. 

"  By  the  above  rules  we  think  the  student  will  be  able,  in 
all  cases,  to  calculate  the  fineness  or  quality  of  his  gold,  and  to 
effect  any  reduction,  whether  ascending  or  descending,  which 
he  may  desire." 

To  facilitate  the  student  in  accurately  compounding  gold 
alloys  from  coins  of  that  metal,  the  following  table,  giving  the 
weight  in  grains,  fineness,  and  the  value  of  the  gold  coins  of 
different  nations,  is  given  in  this  connection. 


ALLOYS  OF  GOLD  FOR  DENTAL  PURPOSES. 


63 


TABLE   OF   COINAGE   OF   DIFFERENT    NATIONS. 


ARGENTINE  EEPUBLIC. 

Doubloon,  Province  of  Rio  de  la  Plata., 
Doubloon,  Province  of  Rio  dt  la  Plata., 


The  same  variation  of  fineness  and  weight 
in  coins  of  the  same  date  are  to  be  found 
in  the  silver  coinage  of  this  republic. 


AUSTRIA. 

Ducat  of  Maria  Theresa 

Sovereign  of  Maria  Theresa 

Ducat  of  Leopold  II 

Ducat  of  Francis  I 

Quadruple  of  Francis  I 

Sovereign  of  Francis  I 

Sovereign  of  Ferdinaud  I  

Half-sovereign  of  Ferdinand  I 

Ducat  of  Ferdinand  I 

Quadruple  of  Ferdinand  I 

Hungary  ducat  of  Ferdinand  I 

BADEN. 

Ten  guilder  (five  guilder  same  quality)  of 
Louis,  Grand  Duke 

BAVARIA. 

Ducat  of  Maximilian  Joseph  and  Charles 

Theodore 

Ducat  of  Maximilian  Joseph  II 

Ducat  of  Louis 

BELGIUM. 

Forty  francs 

Twenty  francs  in  proportion,  same  fine- 
ness. Sovereigns  same  as  Austrian  coin- 
age. 

BOLIVIA. 

Doubloon 

BRAZIL. 

Moidore  of  Maria  I,  and  John  III 

Half-Joe  of  Peter  II 

The  other  moidores  and  half-joes  are  of  the 
same  fineness  with  the  moidore  of  1779, 
varying  slightly  in  weight. 

BRITAIN. 

The  gold  coins  of  this  kingdom  are  of  the 
uniform  finene.ss  of  Sl.'j,.'?,  but  below  the 
legal  standard  about  one  thousandth.  The 
par  value  of  the  pound  sterling  is  about 
84.84.  Sterling  gold  is  worth  94.6  cents 
per  pennyweight. 

BRUNSWICK. 

X.  Thaler  of  Charles 

X.  Thaler  of  Charles  William  Ferdinand... 
X.  Thaler  of  Win.  Fred,  and  George  Regent. 

X.  Thaler  of  Charles „ 

X.  Thaler  of  William 

V.  Thaler  of  Charles 


Year. 


:828-32 
1813-32 


1762 
1778 
1790 
1809-34 
1830 
1831 
1838 
1839 
1838 
1840 
1839 


1819 


1764-97 
1800 
1832 


1779 
1833-38 


174.') 
1805 
18l:i-19 
1824-30 
1831-38 
1748-64 


Weight.  Fineness, 


Grains. 


418 
415 


53.5 
170 

53.5 

53.7 
215.5 
174.5 
174.5 

87 

53.7 
215.5 

53.7 


53 
53 
53.5 


125.5 
221.5 


202 

204 

204.5 

205 

205 

102 


Thous. 
815 


965 
917 
986 
983 
983 
898 
901 
902 
985 
985 
986 


984 
987 


914 
915 


898 
896 
896 
896 
894 
903 


14  66 

15  51 


2  23 

2  24 
2  27 


15  58 


4  94 

8  72   7 


64 


MECHANICAL  DENTISTRY. 


TABLE   OF   COINAGE   OF   DIFFERENT   NATIONS    {continued). 


CENTKAL  AMERICA. 

Doubloons 

CHfLI. 

Doubloons 

Doubloons 

COLOMBIA. 

Doubloon  of  eight  escudos,  Colombia,  Bogo- 

tan  Mint 

Doubloon  of  eight  escudos,  Popayan  Mint. 

Doubloon  of  New  Granada,  Bogota 

Half-doubloon  of  Ecuador,  Quito 

Quarter-doubloon  of  Colombia,  Bogota 

Quarter-doubloon  of  Ecuador,  Quito 

Eighth-doubloon  of  Colombia,  Bogota 

Eighth-doubloon  of  Colombia,  Popayan 

These  last  coins  vary  in  fineness  from  849 
to  854,  and  in  weight  from  44^4  to  613^. 
The  sixteenth-doubloons  are  of  the  same 
quality. 

DENMARK. 

Specie  ducat  of  Frederick  V 

Specie  ducat  of  Christian  VII 

Current  ducat  of  Christian  VII 

Christian  d'or  of  Christian  VII 

Double  Frederick  d'or  of  Frederick  VI 

EGYPT. 

Sequin  fundoukli  of  Achmet  III 

.Sequin  fundoukli  of  Malimoud  I 

Sequin  fundoukli  of  Mahmoud  I 

Sequin  fundoukli  of  Mustapha  III 

Sequin  fundoukli  of  Abdul  Hamed 

Sequin  fundoukli  of  Abdul  Hamed 

Sequin  fundoukli  of  Selim  III 

Half-sequin  fundoukli  of  Mahmoud  II 

Bedidlik,  100  piastres,  of  Abdul  Majeed 

Nusflix,  50  piastres,  of  Abdul  Majeed 

Kairia  Hastreen,  10  piastres,  of  Abdul 
Majeed •. 

The  first  date  given  above  is  the  year  of 
the  Hegira,  the  second,  the  Christian  era. 


FRANCE. 

Louis  d'or  of  Louis  XV 

Louis  d'or  of  Louis  XVI 

Double  Louis  d'or  of  Louis  XV 

Double  Louis  d'or  of  Louis  XVI 

Napoleon,  20  francs,  of  Napoleon 

The  subsequent  gold  coinage  of  France  is 
of  the  uniform  fineness  of  899,  except 
the  twenty  franc  pieces  of  Louis  Phil- 
ippe, coined  in  1840-41,  which  are  900. 

GREECE. 

Twenty  drachms  of  Otho 


Year. 


Weight. 


HANOVER. 

Ducat  of  George  III 


1819-24 
1835  &seq. 


1823-36 

1823-36 
1837 
18.36 

1823-35 
1835 

1823-36 


1749 

1795-1802 

1783 

1775 

1813-39 


1115(1703) 
1143(17.30) 
1143(1730) 
1171(1757) 
1187(1773) 
1187(1773) 
1203(1789) 
1233(1818) 
1255(1839) 
1255(1839) 

1255  (1889) 


1726-73 
1786-92 
1744 
1786-92 
1803-14 


1833 
1776 


Grains. 
417 


417 
417 


416.8 

416.5 

416.8 

209 

104 

104 

51 

51 


53.5 
53.7 
48 

103 

204.5 


53 
39 
39 
39 
39 
39 
39 
18 

132.2 
66.1 

27 


124 
116.5 
250 
235 
99.2 


Fineness.       Value. 


Thous. 
833 


867 
872 


870 
844 
865 
844 
865 
852 


979 
876 
905 
895 


958 
940 

848 
781 
7H6 
645 
690 
670 
874 
875 


897 
900 
902 
901 
899 


900 
993 


d.  c.  m. 
14  96 


15  57 
15  66 


15  61 
15  39 
15  61 


2  27 

2  26 

1  81 

4  01 

7  88 


1  01 


4  79 

4  51 

9  71 

9  11 

3  84 


3  45 

2  28   8 


ALLOYS  OF  GOLD  FOR  DENTAL  PURPOSES. 


65 


TABLE   OF    COINAGE   OF    DIFFERENT    NATIONS    [continued). 


HANOVER  (continued). 

Pistole  or  five  tlialer  of  George  III 

Pistole  or  five  thaler  of  (ieorge  III 

Ten  thaler  of  (ieor^e  Id 

Ten   thaler   of   William  IV,  and    Ernst. 
August 

HESSE. 

Ten  thaler  of  Frederick  II 

Five  thaler  of  Frederick  II 

Five  thaler  of  William  IX 

Five  thaler  of  William  I 

HINDOSTAN. 

Mohurof  B'Tigal 

Mohur  of  Bengal 

Mohur  of  Bengal 

Mohurof  Bengal  

Mohur  of  Madras 

Mohur  of  Bombay 

Half-raohiir  of  Bengal 

Star  pagoda  of  Madras 

Pondiclierry  pagoda  of  Pondicherry 

Porto  Novo  pagoda  of  Portuguese  Company. 


MECKLENBURG  SCHWERIN. 

Ten  thaler  of  Frederick  Francis.... 


MEXICO. 

Doubloon  of  Mexico,  Augustin,  Emperor... 
Doubloon  of  Mexico,  Mexican  Republic 

Other  doubloons  minted  at  Mexico  weigh 
417  grains,  and  are  from  867  to  869  ihou- 
sandthsfioe.  The  doubloon  of  Guanaxu- 
ato  varies  from  860  to  867  in  fineness. 


Doubloon  of  Durango 

Doubloon  of  Durango 

Doubloon  of  Durango 

Doubloon  of  Guadalaxara. 


MILAN. 

I  Zecchino,  or  Sequin,  of  Maria  Theresa  and 

Joseph  II 

I  Doppia,  or  Pi.slole,  of  Joseph  II 

j  Forty  lire  of  Napoleon 

Sovereign  of  Francis  I 

Sovereign  of  Ferdinand  I 

Half-sovereign  


NAPLE.S   AND  SICILY. 

Six  ducat,  of  Ferdinand  IV 

Onzia  of  .'^icily  of  Charles 

Onzia  of  Ferdinand  I 

Twenty  lire  of  Joachim  Napoleon. 


NKTHEBLAKDS. 

Ducat I  1770-1810 

Ducat  of  Williiim  1 

Ten  guilders  of  William  I 


Year. 

Weight. 

Grains. 

1803 

102 

1813-14 

102 

181H-14 

204.5 

1835  &seq. 

205 

1773-8.5 

202 

1771-84 

101 

1788-89 

101.5 

1815-17 

101.5 

1770 

190 

1787 

191 

1793 

191 

1818 

204.7 

1818 

180 

181H 

179 

1787 

9.5 

52.5 

52.5 

52.5 

1831 

204.5 

1822 

416.5 

1824-30 

416.5 

1 

1 

1 
417      1 

417      j 

1833-36 

417.5 

416      ! 

i 

1770-84 

53  5 

1783 

97.5 

180.5-14 

199 

1831 

174  5 

1838 

174.5 

1839 

87 

1783 

135 

1751 

68 

1K18 

68 

.  1813 

99       i 

1770-1810 

1 
53.5    ' 

183:i-39 

53.7 

1816-b9 

103.5 

Fineness. 


Thous. 

896 

.    890 

890 

895 


890 
893 
892 
894 


982 
989 
993 
917 
917 
920 
984 
800 
708 
740 


864 

865 


872 
805 


990 
908 
S99 
898 
901 
902 


893 
9.59 
995 
900 


980 
981 
899 


Value. 


d.  c.  m. 

3  93  6 

3  91 

7  83  8 


7  74  2 

3  88  4 

3  89  9 

3  90  8 


8  03 
8  13 
8  16 


2  28 

3  81 


6  74 
6  77 


15  49   8 
15  51   6 


15  58  8 

15  53  4 

15  67  9 

15  49  7 


66 


MECHANICAL   DEKTISTEY. 


TABLE    OF    COINAGE    OF   DIFFERENT    NATIONS    (continued). 


PERSIA. 

Toman  of  Fatha  Ali  Shah,  Eajar \ 

Toman  of  Mohammed  Shah,  Shakinshah... 
Half-toman  of  Mohammed  Shah 

POLAND. 

Ducat  of  Stanislaus  Augustus 

PORTUGAL. 

Moidore  of  Peter  II 

Moidore  of  Peter  II 

Moidore  of  John  V 

Half-joe 

Half-joe  of  Maria  I,  and  Peter  III 

Half-joe  of  Maria  I 

Half-joe  of  John  VI 

Joannese  of  John  V 

Crown  of  Maria  II 

PRUSSIA. 

Frederick  d'or  of  Frederick  II 

Frederick  d'or  of  Fi-ederiek  William  II 

Frederick  d'or  of  Frederick  Wilhelm  III... 
Double  Frederick  d'or  of  Fred.Wilhelm  III. 
Double  Frederick  d'or  of  Fred.Wilhelm  III. 
Ducat  of  Frederick  William  II 

ROME. 

Sequin  of  Pius  VI 

Doppia  of  Pius  VI 

Doppia  of  Pius  VII 

Gold  scudo  of  Republic 

Ten  scudi  of  Gregory  XVI 

RUSSIA. 

Imperial  of  Elizabeth 

The  gold  coins  of  Russia,  though  irregular 
in  weight,  are  of  the  same  standard  fine- 
ness during  the  reigns  of  Elizabeth  and 
Catharine  II. 

Ducat  of  Paul  I 

Three  roubles  of  Nicholas 

Half-imperial  of  Nicholas 

SARDINIA. 

Pistole  of  Victor  Amadeus,  etc 

Carlino  (island)  of  Victor  Amadeus,  etc 

Marengo  of  Republic 

Eighty  lire 

Genovine  of  Ligurian  republic  (Genoa) 


SAXONY. 

Double  August  d'or  of  Fred.  August.  III... 
Double  August  d'or  of  Fred.  August.  HI... 

Double  Anton  d'or  of  Anthony 

Ducat  of  Anthony 


Year. 

Weight. 

Grains. 

1230-40 

(1814-24) 

1255(1839) 

1252(18.37) 

71.2 
53.7 
27 

1791 

53.5 

1689 

1705 

1714-26 

1727-77 

1778-85 

1787-1804 

1822-24 

1730 

1838 

165 
165 
165 
217 
220 
221 
221 
439 
148 

1752-82 

1795-96 

1799-1812 

1800-11 

1831 

1787 

102 
102 
102 
205 
205 
53.5 

1775-83 
1777-86 

1799 
1836 

525 

84 

84.5 
910 
267.5 

1756 

253 

1798 
1838 
1839 

66 
60.5 
100.5 

1773 
1800 

1798 

148 
247 
98 
398 
888 

1784-1817 

1826 

1830-36 

1830 

204.5 
205 
205 
53.7 

Fineness. 


Thous. 


991 
966 
9ii8 


928 
913 
914 
913 
914 
909 
912 
912 


901 
897 
91)1 
898 
903 
979 


996 
906 
901 
833 
900 


915 


969 

917 
917 


905 
890 


900 
979 


Value. 


6  45 

6  59 

6  48 

8  62 

8  65 

8  69 

8  65 

17  24 

5  81 


2  25 

3  27 
3  27 

32  64 

10  36 


9  97 


2  75   4 

2  38   9 

3  96   9 


5  76 

9  46 

3  79 

15  39 

15  17 


7  89  1 

7  92  8 

7  94  6 

2  26  4 


AI  LOYS  OF  GOLD  FOR  DENTAL  PURPOSES. 


67 


TABLE   OF   COINAGE   OF    DIFFERENT   NATIONS    (continued). 


Cob  doubloon  of  Philip  V,  American 

Doubloon  of  Ferdinand  VI,  American 

Doubloon  of  Charles  III,  AiuericaD 

Doubloon  of  Charles  III,  Spanish 

DoublooQ   of  Charles  IV,  and  Ferdinand 

VII,  American 

Pistole  of  Philip  V,  Spanish 

Pistole  of  Charles  III,  American 

Pistole  of  Ferdinand  VII,  American 

Escudo  of  Charles  III,  Spanish 

Escudo  of  Charles  IV 

Escudo  of  Ferdinand  VII,  American 

Half-doubloon  of  Charles  III,  Spanish 

Half-doubloon  of  Charles  IV,  American.... 
Ualf-doubloon  of  Ferdinand  VII,  Spanish. 

SWEDEN. 

Ducat  of  Gustavus  III,  and  Gustavus  IV... 
Ducat  of  Charles  John  XIV 

SWITZERLAND. 

Pistole  of  Berne 

Pistole  of  Basle 

Pistole  of  Soleure 

Pistole  of  Helvetian  Republic 

Ducat  of  Berne 

Ducat  of  Basle 

TUNIS. 

Half-sequin  of  Abdul  Hamed 

TURKEY. 

Sequin  fondouk  of  Selim  III 

Sequin  zermahboub  of  Selim  III 

Obikilik  of  Mahmoud  II 

Twenty  piastres,  of  Mahmoud  II 

Yirmilik,  20  piastres  of  Abdul  Medjid 

TUSCANY. 

Ruspone  of  Francis  III,  to  Leopold  III 

Ruspone  of  Louis  I,  and  Charles  I 

Ruspone  of  Leopold  II 

Sequin  of  Leopold 

Sequin  of  Leopold  II 

UNITED  STATES. 

Eagle 

Eagle 

Eagie 

WURTEMBERO. 

Ducat  of  Charles 


17.3.3-44 

17.51 
1772-84 
1786-88 

1789-1821 

174.5 

1774-82 

1813-24 

17S6-88 

1789-1808 
1809-20 
1780-82 

1789-1808 
1810-24 


1777-1800 
1838 


Weight, 


Grains, 

416 
416 
416 
416 

416.5 
103 
103 
104 

52 

52 

52 
206 
208 
208 


17961     116 
1795     118 


1798, 
1800 
1794 


1789 
1789 
1822-24 
1827 
1840 


1738-1800 
1801-07 
1824-34 
1765-79 
1824-34 


1792-18341 

1834-371 

1837  &seq. 


116 
116 

52.5 

53 


1773       19 


52.5 

36 

25 

27.5 

24.5 


160 
161 
161 

53 

53.5 


270 
258 
258 


53 


Fineness, 


Thous. 

895* 
908 
843t 
890 


909 
895 
872 
874 
868 
851 
896 
870 
865 


977 
975 


901 
891 
898 
897 
974 
943 


800 
800 
833 
875 
832 


997 
998 
999 
997 
999 


916.7 
899.2 
900 


980 


Value, 


d.  c.  m. 

16  03  4 

16  26  5 

16  00 

15  58  7 

15  57 


10  67 
9  99 
10 


1    80  9 
1    24 

89  7 

1    03-  7 

87  7 


*  Varies  from  893  to  898.       t  Varies  from  883  to  893,  the  oldest  pieces  being  the  best. 


MECHANICAL,   DENTISTRY. 


CHAPTER  V. 

Method  of  Converting   Gold  Alloys  into  the  Re- 
quired Forms  for  Dental  Purposes, 

Manner  ofProeuring  an  Ingot. — The  gold,  with  its  alloying 
constituents,  is  put  into  a  clean  crucible,  lined  on  the  inside 
with  borax,  and  placed  in  the  furnace.  When  the  contained 
metals  are  perfectly  fused,  the  crucible  should  be  removed 
from  the  fire  with  a  pair  of  tongs,  and  the  contents  poured 
quickly  but  carefully  into  the  ingot  moulds ;  the  latter  being 
placed  conveniently  near  the  mouth  of  the  furnace,  as  the 
molten  metals  soon  become  chilled  on  exposure  to  the  open 
air.  Before  pouring,  the  moulds,  if  made  of  iron,  should  be 
moderately  heated  and  oiled,  or  coated  with  lamp-smoke  by 

Fig.  22. 


holding  their  inner  surfaces  over  the  flame  of  an  oil-lamp  or 
gas-jet. 

Ingot-moulds  are  constructed  of  various  substances,  but 
those  in  most  common  use,  and,  at  the  same  time,  most  conve- 
nient, are  formed  of  iron,  and,  for  gold,  are  generally  about 
two  inches  square  and  from  one-eighth  to  one-sixth  of  an  inch 
thick.     (Fig.  22.)     They  should  be  slightly  concave  on  their 


CONVERTING    GOLD   ALLOYS    INTO   REQUIRED    FORMS.      69 

inner  surfaces  to  compensate  for  the  greater  shrinkage  of  the 
gold  in  the  centre  than  at  the  margins  of  the  ingot. 

A  very  ingenious,  convenient,  and  useful  contrivance,  com- 
bining crucible  and  ingot-mould,  and  by  the  use  of  which  in- 
gots of  gold,  silver,  etc.,   may   be  quickly 
obtained  without  the  use  of  a  furnace,   is  fig.  23. 

shown  in  Fig.  23.  The  crucible  (A)  is  of 
moulded  carbon,  and  is  supported  in  position 
by  an  iron  side-plate.  The  ingot  mould  is 
indicated  by  the  letter  C.  The  letter  D 
shows  clamp  holding  crucible  and  ingot 
mould  in  position,  and  swivelling  on  the  cast-iron  stand,  B. 

The  metal  to  be  melted  is  placed  in  the  crucible,  and  the 
flame  of  a  blowpipe  is  directed  on  it  until  it  is  perfectly  fused. 
The  waste  heat  serves  to  make  the  ingot  mould  hot,  and  the 
whole  is  tilted  over  by  means  of  the  upright  handle  at  the 
back  of  the  mould.  With  this  simple  instrument  a  sound 
ingot  may  be  obtained  at  any  time  in  about  two  minutes. 

Soapstone  is  sometimes  employed  for  the  same  purpose,  and 
is  preferred  by  many.  It  should  also  be  warmed  and  oiled 
before  pouring  the  metals.  Moulds  made  from  charcoal  are 
also  sometimes  used,  but,  as  they  require  to  be  frequently 
renewed,  are  not  generally  employed.  Moulds  are  formed 
from  this  latter  substance  by  selecting  two  pieces  with  even 
surfaces  or  dividing  a  single  piece  with  a  saw,  when  either  the 
required  size  and  shape  of  the  mould  may  be  cut  out  in  one 
half,  or  a  strip  of  sheet-iron  a  little  broader  than  the  required 
thickneas  of  the  iugot,  being  bent  into  proper  form,  is  placed 
between,  and  the  edges  partially  iml>edded  in  the  two  pieces  of 
charcoal,  and  the  latter  secured  by  binding  them  together  with 
wire.  Moulds  made  from  this  material  do  not  require  to  be 
either  heated  or  oiled. 

It  not  unfrequently  happens  that,  at  the  first  pouring,  the 
metals  arrange  themselves  in  the  ingot  in  accordance  with  the 
density  of  the  several  components ;  those  of  greater  specific 
gravity  passing  to  the  bottom,  and  the  lighter  metals  remain- 
ing above.     Whenever  this  occurs  the  ingot  must  be  broken 


70 


MECHANICAL    DENTISTEY. 


into  pieces  and  remelted ;  this  should  be  repeated,  if  necessary, 
until  the  alloy  assumes  a  perfectly  homogeneous  appearance. 
It  should  then  be  annealed  in  hot  ashes,  which  softens  the 
gold  and  removes  the  adhering  grease. 

Forging. — Before  laminating  the  ingot  it  should  be  reduced 
somewhat  in  thickness  by  placing  it  on  an  even-faced  anvil  or 
other  equally  smooth  and  resistant  surface,  and  subjecting  it  to 
repeated  blows  with  a  tolerably  heavy  hammer.  It  should  be 
frequently  annealed,  and  the  process  of  forging  continued, 
alternately  hammering  and  annealing,  until  the  ingot  is  reduced 
one-half  or  more  in  thickness. 

Laminating  or  Rolling. — The  reduced  ingot,  well  annealed, 
is  next  laminated  or  spread  out  into  a  sheet  of  greater  or  less 
thinness  by  passing  it  repeatedly  between  two  strong,  highly- 


Fltt.  25. 


polished,  cylindrical  steel  rollers.  The  mills  used  for  the  pur- 
pose are  variously  constructed,  the  plainest  forms  (Fig.  24)  be- 
ing very  simple  in  their  mechanism,  while  others,  or  geared 
mills,  are  more  complicated,  and  are  constructed  with  a  view 
to  a  greater  augmentation  of  power,  and  precision,  and  cer- 
tainty of  action.  The  latter  (Figs.  25,  26),  if  of  approved  pat- 
tern, materials,  and  manufacture,  are,  upon  the  whole,  more 
economical  and  reliable  than  the  cheaper  varieties.  The  rollers, 
for  the  purposes  of  the  dentist,  should  be  from  three  to  four 
inches  in  length. 


COXVERTING    GOLD    ALLOYS    INTO    REQUIRED    FORMS.       71 

In  laminating,  the  rollers  should  first  be  adjusted  equidis- 
tant at  both  ends,  and  this  uniformity,  as  they  are  approxi- 
mated from  time  to  time,  should  be  preserved  throughout. 
At  every  passage  of  the  gold  bar  between  the  rollers  the  dis- 
tance between  the  latter  should  be  diminished,  care  being  taken 
that  the  approximation  be  not  sufficient  to  clog  or  impede  the 

Fig.  26. 


free  action  of  the  mills.  The  gold,  which,  in  time,  becomes 
hard,  and  brittle,  and  liable  to  crack  in  the  mills,  should  be 
frequently  and  well  annealed  by  bringing  it  to  a  full  red  heat; 
this  restores  the  pliancy  of  the  gold  and  facilitates  the  opera- 
tion in  the  press. 

When  the  ingot  has  been  extended  in  one  direction  as  far 
as  may  be  desired,  it  should  always  be  re-annealcd   before 


72 


MECHAlvICAL  PENTTIBTEY. 


FiG-  27. 


tamino::  it  in  the  mills ;  a  neglect  of  this  precaution  will  seri- 
ously interfere  with  the  working  of  the  gold  by  twisting  or 
doubling  the  plate  upon  itself;  and  in  some  instances,  pro- 
vided the  gold  has  not  been  well  annealed  throughout  the 
operation,  or  is  in  any  considerable  degree  unmalleable,  the 
plate  wiD  be  torn  across  and  rendered  unfit  for  use. 

A  thin  or  retreating  edge  may  be  given  to  the  plate  at  any 
desired  point  or  points  by  passing  such  portions  part  way 
between  the  rollers  and  withdrawing  ;  repeating  this,  with  the 
rolleis  brought  a  little  nearer  to  each  other  every  time  the  plate 
is  introduced  between  them,  and  decreasing  the  distance  the 
plate  passes  each  time  until  it  is  reduced  to  as  thin  an  edge  as 
may  be  d^ired. 

The  degree  of  attenuation  obtained  by  rolling  is  determined 

by  what  is  called  a  gauge-plate, 
(Fig.  27.)  Tills  instrument  is 
usually  circular  or  oblong  in  form, 
and  is  marked  at  intervals  on  its 
edge  by  cross-cut  grooves  or  fis- 
'^-i  sures,  which  successively  dimin- 
ish in  size  and  are  indexed  by 
numbers  ranging  from  6  to  40. 
The  size  of  the  grooves  diminish 
with  the  ascending  numbers. 
During  the  operation  of  rolling, 
the  plate  should  be  tested,  from  time  to  time,  by  the  gauge,  to 
determine  when  it  has  undergone  sufficient  attenuation. 

Thichiess  of  Gold  Plate  required  as  a  Base  for  Artificial 
BaitureB. — ^In  prescribing  the  thickness  of  plate  proper  for 
the  puq>ose  indicated,  no  estimate  can  be  given  that  will 
apply  to  all  cases,  as  certain  conditions  of  the  mouth,  to  be 
mentioned  hereafter,  will  suggest  some  modifications  in  this 
lespect.  Usually,  however,  plate  for  entire  upper  sets  should 
correspond  in  thickness  with  number  26  of  the  gauge-plate ; 
for  the  under  jaw,  number  24  may  be  used  ;  while  for  partial 
upper  pieces,  an  intermediate  number  may  be  chosen,  unless 


CONVERTING    GOLD    ALLOYS    INTO    REQUIRED    FORMS.       73 

atmospheric-pressure  plates  are  used,  when  the  number  recom- 
mended for  full  upper  sets  may  be  employed. 

Thickness  of  Plate  for  Clasps,  Stays,  etc. — Plate  for  these 
purposes  should  correspond  with  from  20  to  22  of  the  gauge ; 
a  less  amount  of  substance,  as  before  stated,  being  required 
when  the  alloy  has  incorporated  with  it  a  small  proportion  of 
platinum. 

lied  action  of  Gold  Solders  into  Proper  Form  for  Use. — The 
method  of  converting  gold  solders  into  the  form  of  plate,  does 
not  differ  from  that  already  described  in  the  manufacture  of 
plate  as  a  base,  except  that  when  zinc  or  brass  is  used,  the 
latter  should  be  added  after  the  other  constituents  are  com- 
pletely fused,  and  then  instantly  poured  to  prevent  undue 
wasting  of  the  base  metals  by  a  too  protracted  heat. 

The  solder  should  be  reduced  to  plate  somewhat  thinner 
than  that  used  for  upper  sets,  28  of  the  gauge-plate.  It  is 
customary  sometimes  to  roll  the  solder  into  very  thin  rib- 
bons, but  this  is  objectionable  for  the  reason  that  a  greater 
amount  of  the  alloying  metals  being  exposed  in  a  given  sur- 
face to  the  action  of  the  heat  in  soldering,  are  burnt  out  or 
oxidated,  whicli  interrupts  the  flow  and  weakens  the  attach- 
ment between  the  solder  and  plate.  / 

Method  of  Obtaining  Gold  Wire. — To  convert  gold  or  its 
alloys  into  the  form  of  wire,  the  operator  should  be  provided 
with  a  draw-plate,  a  vice,  and  a  pair  of  hand-pincers.  A 
draw-plate  (Fig.  28)  is  an  oblong  piece  of  steel  pierced  with  a 
regular  gradation  of  holes,  or  a  series  of  progressively  dimin- 
ishing apertures,  through  which  the  gold  bar,  reduced  to  a 
rod,  is  forced  and  made  to  assume  the  form  and  dimensions 
of  the  hole  through  which  it  is  last  drawn.  The  holes  are 
formed  with  a  steel  punch,  and  are  enlarged  on  the  side 
where  tlie  wire  enters  and  diminish  with  a  gradual  taper  to 
the  other  side.  A  draw-bench  is  sometimes  employed  in  ex- 
tending the  wire,  the  power  being  applied  by  a  toothed  wheel, 
pini<;n,  and  rack-worK,  and  is  moved  by  the  hands  of  one  or 
two  persons.  For  the  purposes  of  tlie  dentist,  however,  it 
will  be  sufficient  to  fix  the  draw-plate  securely  between  the 


74  MECHANICAL,   DENTISTRY. 

jaws  of  a  bench-vice,  and,  by  seizing  hold  of  one  end  of  the 
gold  rod  with  a  strong  pair  of  clamps  or  hand-pincers,  serrated 
or  cut  like  a  file  on  the  inside  of  the  jaws,  the  wire  may  be 
drawn  steadily  through  the  plate,  passing  from  the  larger  to 
the  smaller  holes  until  a  wire  of  the  required  size  is  obtained. 


Fig.  28. 

6'.v 

5^ 

VV 

fc-^^ 

0 

^,^ 

.) 

c) 

Cv 

0O 

• 

^) 

'<.•) 

I  • 

k)© 

<^ 

^ 

(!J>C 

'^^ 

«® 

■d^gss- 

In  drawing  the  wire,  the  motion  should  be  steady  and  uni- 
form, for  if  drawn  interruptedly  or  by  jerks,  the  wire  will  be 
marked  by  corresponding  inequalities.  The  gold  rod  should 
also  be  annealed  from  time  to  time,  and  the  holes  kept  well 
greased  or  waxed. 

The  process  described  above  will  answer  equally  well  in  re- 
ducing any  of  the  ductile  metals  to  wire,  as  silver,  copper, 
platinum,  etc.,  so  that  any  further  description  of  the  method, 
in  connection  with  these  metals,  will  be  unnecessary. 

Method  of  Constructing  Spiral  Springs. — Inasmuch  as  spiral 
springs  have  been,  to  a  great  extent,  superseded  by  more  ap- 
proved agencies  employed  in  the  retention  of  artificial  teeth  in 
the  mouth,  and  as  all  the  principal  dental  furnishing  houses 
are  suppled  with  these  appliances  already  prepared  for  use, 
the  author  does  not  deem  it  necessary  to  enter  into  a  descrip- 
tion of  the  various  apparatuses  used  in  making  them. 

The  following  simple  contrivance  will  meet  the  limited  re- 
quirements of  those  who  are  obliged  or  prefer  to  manufacture 


CONVERTING   GOLD   ALLOYS    INTO    REQUIRED    FORMS.       75 

their  own  springs.  The  wire,  obtained  as  already  described, 
is  held  between  two  blocks  of  wood  fastened  between  the  jaws 
of  a  bench-vice.  By  means  of  a  small  hand-vice,  one  end  of 
the  wire  is  clamjied  to  a  uniformly  cylindrical  and  well-tem- 
pered steel  rod  or  wire  four  or  six  inches  long,  and  about  the 
size  of  a  small  knitting  needle,  and  which  being  made  to  re- 
volve while  resting  on  the  blocks  of  wood,  the  wire  is  wound 
firmly  and  compactly  around  it,  producing  a  uniform  coil. 


76  MECHANICAL   DENTISTRY. 


CHAPTER  yi. 

Silver. 

General  Properties  of  Silver. — Pure  silver,  when  planished, 
is  the  brightest  of  the  metals.  Fused,  or  in  the  form  of  ingot, 
its  specific  gravity  is  10.47 ;  but  when  hammered  or  condensed 
in  the  coining  press,  its  density  is  increased,  and  its  specific 
gravity  becomes  10.6.  It  fuses  at  an  extreme  red  heat,  gener- 
ally estimated  at  1.873°  Fahrenheit.  It  is  remarkably  lamin- 
able  and  ductile;  yielding  leaves  not  more  than  _-j_'__^  of  an 
inch  thick,  and  wire  400  feet  of  which  may  be  drawn  weighing 
but  a  single  grain.  It  exceeds  gold  in  tenacity  or  cohesion, 
but  is  inferior  to  platinum  in  this  respect.  A  silver  wire  .078 
of  an  inch  in  diameter  will  sustain  a  weight  of  187.13  pounds. 
Fine  silver  is  unaffected  by  moisture  or  pure  atmospheric  air, 
but  is  readily  tarnished  with  a  film  of  brown  sulphuret  by  ex- 
posure to  sulphuretted  hydrogen.  The  sulphuret  of  silver 
thus  formed  may  be  easily  removed  by  rubbing  the  metal  with 
a  solution  of  cameleon  mineral,  prepared  by  calcining  equal 
parts  of  black  or  peroxide  of  manganese  and  nitre.  Unlike 
gold  and  platinum,  it  is  readily  soluble  in  nitric  acid ;  this  and 
sulphuric  acid  being  the  only  simple  ones  that  dissolve  it. 
Silver  becomes  very  brilliant  when  heated ;  boils  and  vaporizes 
above  its  fusing-point ;  and  when  cooled  slowly,  its  surface 
presents  a  crystalline  appearance. 

Alloys  of  Silver. — Silver  combines  readily  with  most  metals, 
forming  compounds  of  variable  degrees  of  malleability,  duc- 
tility, density,  etc. 

Tin,  zinc,  antimony,  lead,  bismuth  and  arsenic,  render  it 
brittle.  A  very  minute  quantity  of  tin  is  fatal  to  the  ductility 
of  silver.  Silver  does  not  easily  combine  with  iron,  although 
the   two   metals   may  be   united   by  fusion.      Gold,  copper, 


SILVER.  77 

platinum,  iridium,  steel,  manganese,  and  mercury,  also  form 
alloys  with  silver. 

An  alloy  of  nine  parts  of  silver  and  one  of  copper  is  the 
Government  standard  of  the  United  States  coinage  since  1837. 
To  this,  three-cent  pieces  form  an  exception;  these  being  com- 
posed of  three  parts  silver  and  two  of  copper.  The  coins  of 
silver  having  a  greater  average  fineness  than  those  of  <Hir  own 
country,  are  Brazil,  Britain,  Chili,  France,  Greece,  Hindostan, 
Persia,  Portugal,  Rome,  and  Tuscany.  A  common  impression 
prevails  that  the  Mexican  silver  coin  contains  more  than  an 
average  percentage  of  silver,  and  is  therefore  sought  after  on 
account  of  its  supposed  purity.  This  is  true  of  some  pieces 
coined  at  different  periods,  but  the  average  fineness  of  the 
Mexican,  as  well  as  Spanish  coins,  is  exceeded  by  those  of  the 
United  States  mints. 

Reduction  of  Silver  to  the  Required  Forms  for  Dental  Pur- 
poses.— Owing  to  the  very  soft  and  flexible  nature  of  silver  in 
its  pure  state,  it  is  usual,  when  converting  it  into  plate  or  other 
forms  for  use,  to  employ  an  alloy  of  the  metal.  Hence  silver 
coins,  which  are  made  harder  by  the  copper  they  contain,  are 
generally  selected  for  the  purpose.  The  employment  of  silver, 
thus  debased,  as  a  base  for  dental  substitutes  is  regarded  by 
many  as  unsafe  and  injudicious.  Although  the  influences  of 
an  alloy  so  readily  acted  upon  as  this  by  the  various  agents 
which  affect  it  chemically,  cannot  always  be  certainly  predicted 
in  every  case,  yet  no  reasonable  doubt  can  be  entertainerl  but 
that,  under  the  favoring  conditions  which  usually  exist  in  the 
mouth,  the  evils  accruing,  directly  and  indirectly,  to  the  organs 
of  the  mouth,  and  through  them  to  the  general  system,  are 
positive  and  undoubted.  If  used  at  all,  therefore,  it  should  be 
alloyed  with  the  least  practicable  amount  of  copper,  or  what  is 
better,  pure  silver  should  be  reduced  with  platinum  alone,  in 
sufficient  quantities  to  impart  to  the  plate  an  adequate  degree 
of  strength  and  elasticity.  The  tendency  of  silver  to  tarnish 
in  the  mouth  when  alloyed  with  copper,  may  be  diminished  by 
boiling  the  finished  piece  in  a  solution  of  cream  of  tartar  and 
chloride  of  soda,  or  common  salt,  or  by  scrubbing  it  with  aqua 


78  MECHANICAL   DENTISTEY. 

ammonia,  which  removes  the  superficial  particles  of  copper,  and 
exposes  a  surface  of  fine  silver.  When  platinum  is  introduced 
as  the  sole  alloying  component,  the  purity  of  the  silver  is  not 
only  preserved,  but  the  alloy  is  less  easily  acted  on  chemically, 
while  the  plate  derived  from  it  is  rendered  sufficiently  inflexible 
and  elastic.  From  three  to  five  grains  of  platinum  may  be 
added  to  one  pennyweight  of  pure  silver. 

On  account  of  the  strong  affinity  of  sulphur  for  silver,  the 
fuel  most  proper  to  be  used  in  melting  it  is  charcoal.  The 
various  processes  employed  in  the  conversion  of  silver  into  the 
required  forms  for  use  are  similar  to  those  described  for  gold, 
and  need  not  be  recapitulated. 

Formulas  for  Silver  Solders. — Silver  solders  are  usually 
composed  of  silver,  copper,  and  zinc,  in  variable  proportions. 
Alloys  formed  from  the  following  formulas  are  such  as  are 
generally  employed  in  soldering  silver  plate  derived  from  the 
coins  of  that  metal.  Three-cent  pieces,  composed  of  two 
parts  silver  and  one  of  copper,  may  also  be  used  for  the  same 
purpose. 

Formula  No.  1.  Formula  No.  2. 

Silver,  .         .     66  parts.  Silver,         .         .     6  parts. 

Copper,       .         .     30      "  Copper,        .        .     2      " 

Zinc,  .         .     10      "  Brass,  .         .     1      " 

When  the  material  to  be  united  is  composed  of  pure  silver 
and  platinum,  silver  coin  alloyed  with  one-tenth  zinc  may  be 
used  as  a  solder. 

In  compounding  silver  solders,  the  silver  and  copper  should' 
be  first  melted,  and  the  zinc  or  brass  afterwards  added,  when 
they  should  be  quickly  poured  to  prevent  undue  waste,  by 
oxidation,  of  the  more  fusible  com23onent.  The  ingot  when 
cold,  should  be  rolled  into  a  plate  a  little  thicker  than  that 
recommended  for  gold  solder. 


PLATINUM    AXD    THE    PLATINOID    METALS. 


CHAPTER  VII. 

Platinum  and  the  Platinoid  Metals. 

Platinum  is  a  grayish-white  metal,  resembling  in  some 
measure  polished  steel.  It  is  harder  than  silver,  and  has  a 
density  greater  than  any  other  known  metal,  its  specific  gravity 
beino-  21.25.  It  remains  unaltered  in  the  highest  heat  of  a 
smith's  forge,  and  can  only  be  fused  by  means  of  the  oxy- 
hydrogen  blow-pipe  and  galvanism.  A  white  heat  does  not 
tarnish  it,  nor  is  it  in  any  way  affected  by  exposure  either  in 
the  air  or  water.  It  is  insoluble  in  any  of  the  simple  acids  ; 
nitro-muriatic  acid  being  the  only  one  that  dissolves  it.  It 
is  sufficiently  malleable  to  be  hammered  into  leaves  so  thin  as 
to  be  blown  about  by  the  breath.  It  may  be  drawn  into  wire 
the  two-thousandth  of  an  inch  in  diameter,  and  a  still  greater 
attenuation  may  be  obtained  by  coating  the  wire  with  silver, 
drawing  it  out,  and  dissolving  off  the  latter  metal. 

Platinum  is  very  soft  and  flexible,  and  when  rolled  into 
thin  sheets,  say  28  or  30  of  the  gauge-plate,  and  well  annealed 
at  a  strong  white  heat  for  eight  or  ten  minutes,  it  may  be 
readily  forced  into  all  the  inequalities  of  a  zinc  die  without 
producing  any  appreciable  change  in  the  face  of  the  latter. 

The  following  interesting  and  practical  observations  on  the 
method  of  melting  and  welding  platinum  scraps  are  taken 
from  a  recent  dental  publication,*  by  E.  A.  L.  Roberts.  By 
this  process,  the  operator  will  be  enabled  to  re-convert  his 
wa-ste  scraps  of  platinum  into  convenient  forms  for  use,  and 
which  he  could  not  otherwise  avail  himself  of  on  account  of 
the  infusible  nature  of  this  metal  in  its  uncombined  state. 

"  Platinum  used  by  dentists  should  be  soft,  tough,  and 
without    flaws.      These   qualities   can    be    attained    only    by 

*  Dental  Instructor,  vol.  i,  p.  10. 


80  MECHANICAL    DENTISTRY. 

thorough  melting  and  welding.  The  welding  must  be  done 
at  a  white  heat.  When  the  surface  is  cool  enough  to  be 
visible,  the  metal  is  too  cool  to  be  welded,  and  every  blow  is 
injurious,  because  it  has  a  tendency  to  shatter  and  shake  it  to 
pieces.  The  necessary  delicacy  of  this  process,  and  the  uncer- 
tainty of  success,  has  led  some  writers  to  declare  that  platinum 
is  incapable  of  being  welded.  The  platinum  must  be  per- 
fectly clean,  and  must  be  heated  in  a  muffle.  When  welded, 
the  metal  should  be  handled  with  tongs  plated  with  platinum, 
and  hammered  with  a  clean  hammer  on  a  clean  anvil,  both  of 
which  should  be  as  hot  as  possible,  without  drawing  the 
temper  of  the  steel.  The  hammer  used  in  welding  should 
weigh  about  a  pound,  to  prevent  drawing  the  metal ;  but 
when  welded,  the  metal  may  be  forged  with  a  heavier  ham- 
mer. 

"The  scraps  or  sponge  should  be  condensed  in  a  square 
mould,  very  compactly,  two  pieces  of  which,  weighing  from  ten 
to  twenty  ounces,  may  be  put  into  a  muffle  together.  When 
the  heat  becomes  so  great  that  on  opening  the  door  the  metal 
becomes  invisible,  bring  one  of  the  pieces  in  the  tongs  quickly 
to  the  anvil,  give  it  three  or  four  quick,  sharp  blows,  in  rapid 
succession.  Return  the  piece  to  the  muffle,  and  proceed  with 
the  other  piece  in  like  manner,  and  thus  alternately  till  both 
are  thoroughly  welded. 

"  We  use  one  of  our  improved  tooth -furnaces  of  the  largest 
size,  fourteen  by  ten  inches,  inside  measure. 

"  Platinum  should  never  be  thrown  into  water  while  hot, 
as  that  tends  to  make  it  crystallize.  It  should  be  thoroughly 
hammered,  as  it  makes  it  tough  and  fibrous.  The  following 
process  gives  the  best  results  in  melting  this  metal.  Condense 
the  scraps,  sponge  or  filings  in  an  iron  mould.  Lay  the  con- 
densed mass  on  a  concave  tire-brick,  and  heat  it  to  whiteness. 
Take  the  brick  from  the  muffle,  and  place  it  in  a  sheet-iron 
pan,  coated  with  plaster  and  asbestos.  The  pan  should  be 
deep  enough  and  broad  enough  to  catch  all  the  globules  and 
other  loose  particles  of  the  metal.  Place  it  under  the  jet  of 
the  oxy-hydrogen  blowpipe,  in  the  following  manner  : 


PLATINUM    AND    THE    PLATIXOID    METALS.  81 

"  The  pan  is  provided  with  a  handle,  opposite  to  which  is  a 
ring,  which  is  to  be  attached  to  an  iron  hook  and  rod,  sus- 
l^ended  from  the  ceiling  by  a  slip  of  india-rubber,  which  en- 
ables the  operator  to  hold  the  pan  conveniently  at  any  distance 
from  the  jet  of  the  burning  gases.  The  hydrogen  is  first 
lighted,  and  gives  a  powerful  flame,  but  as  the  oxygen  com- 
bines with  it,  the  flame  subsides  into  an  intense  focus  of  heat, 
in  which  the  metal  is  soon  brought  to  a  state  of  fusion. 
Begin  at  one  end  and  melt  along  towards  the  other,  till  the 
whole  is  fused  in  one  mass.  The  platinum  in  this  condition, 
when  cool,  is  quite  crystallized  and  sonorous.  It  breaks  very 
easily,  like  spelter-zinc.  Heat  it  very  hot  and  forge  it.  A 
continuatior;  of  this  process  renders  it  soft,  tough,  and  fibrous. 
When  reduced  to  the  width  desired,  and  to  the  thickness  of 
one-fourth  of  an  inch,  it  should  be  made  very  hot,  and  passed 
instantly  through  the  rollers." 

Platinum,  in  mechanical  practice,  is  chiefly  employed  as  a 
base  for  continuous  gum  work ;  it  is  also  used  as  a  coloring 
ingredient  of  porcelain,  and  for  pins  in  the  manufacture  of 
mineral  teeth ;  and,  to  a  limited  extent,  in  some  of  the  minor 
operations  of  the  shop. 

Pure  gold  is  the  only  proper  solder  for  this  metal. 

Alloys  of  Platinum. — Platinum  unites  with  most  of  the 
base  metals,  forming  alloys  of  variable  degrees  of  hardness, 
elasticity,  brittleness,  color,  fusibility,  etc.,  but  their  practical 
value  to  the  dentist  is  not  sufficient  to  justify  a  separate 
description  of  their  properties. 

Alloyed  with  gold  it  forms  a  straw-colored  alloy,  the  shade 
depending  on  the  quantity  of  gold  added.  Silver  hardens  it, 
the  resulting  alloy  being  unaffected  by  sulphur. 

Platinoid  3fetals. — The  platinoid  metals,  palladium,  iridium, 
osmium,  rhodium,  and  ruthenium,  are  native  contaminations, 
the  alloys  of  these  metals  having  a  close  general  resemblance 
to  platinum. 

Among  the  platinoid  metals,  palladium  is  the  only  one  that 
has  been  used  for  dental  purposes,  and  that  only  to  a  limited 
extent.     It  is  of  a  steel-gray  color,  and  when  planished,  is  a 


82  MECHANICAL   DENTISTEY. 

brilliant  steel- white  metal  not  liable  to  tarnish  in  the  air. 
Though  closely  resembling  platinum,  it  may  be  readily  distin- 
guished from  the  latter  metal,  by  the  following  tests:  1.  It 
has  little  more  than  one-half  the  density  of  platinum.  2.  If  a 
piece  of  it  is  heated  to  redness,  it  assumes  a  bronze-blue  shade 
of  greater  or  less  intensity,  as  it  is  cooled  more  or  less  slowly; 
but  if  it  is  suddenly  chilled  by  immersing  it  in  cold  water,  it 
instantly  resumes  its  original  lustre.  3.  When  a  drop  of  the 
tincture  of  iodine  is  let  fall  upon  its  surface  and  evaporated 
over  the  flame  of  a  lamjD,  a  black  spot  remains,  which  does 
not  occur  with  platinum.  Palladium  melts  at  about  9500° 
Fahrenheit,  and  does  not  oxidize  at  a  white  heat.  Its  specific 
gravity  is  from  11.8  to  12.14. 


ALUMINUM.  83 


CHxlPTER  YIII. 

Aluminum. 

Aluminum  is  the  metallic  basis  of  alumina,  the  latter  being 
the  characteristic  ingredient  of  common  clay.  It  is  only  within 
the  past  few  years  that  the  attention  of  chemists  has  been  di- 
rected to  the  production  of  this  remarkable  metal  with  a  view 
to  its  general  introduction  into  commerce  and  the  arts.  Prior 
to  the  researches  of  M.  Deville,  who,  under  the  patronage  of 
the  then  Emperor  of  the  French,  commenced  his  researches 
in  1854  for  the  production  of  this  metal  on  a  large  scale,  the 
small  quantities  produced  and  the  corresponding  exorbitant 
prices  it  commanded,  rendered  it  entirely  unavailable  for  other 
purposes  than  merely  scientific  experiment.  The  improve- 
ments in  the  methods  of  obtaining  it,  however,  which  have 
been  recently  introduced,  cannot  fail,  by  rendering  its  produc- 
tion more  economical,  to  supply  it  in  much  larger  quantities 
and  at  a  corresponding  reduction  in  the  cost  of  the  metal. 

The  following  account  of  the  properties  of  this  metal  is 
taken  from  a  paper  read  before  the  Society  of  Arts,  London, 
by  its  Secretary,  P.  Le  Xeve  Foster.  It  embodies  the  most 
authentic  and  complete  description  of  the  properties  of  alu- 
minum that  has  yet  been  published. 

"One  of  the  most  striking  properties  of  aluminum  is  its  ex- 
treme lightness,  its  specific  gravity  being  2.6,  nearly  that  of  glass, 
whilst  that  of  platinum  is  21.5,  gold  19.5,  silver  10.5,  copper 
8.96,  zinc  7.2,  tin  7.3. 

"The  metal  is  malleable,  ductile,  almost  without  limit;  it 
can  be  reduced  to  very  thin  sheets,  or  drawn  into  very  fine 
threads.  Its  tenacity,  though  su])erior  to  that  of  silver,  is  less 
than  that  of  copper ;  but  no  very  accurate  experiments  have 
been  made  in  this  respect. 


84  MECHANICAL   DENTISTRY. 

"When  pure  it  is  about  as  hard  as  silver.  Its  elasticity  is 
not  great.  It  files  readily,  and  is  said  not  to  injure  the  file. 
It  conducts  electricity  with  great  facilty,  so  that  it  may  be  con- 
sidered as  one  of  the  best  conductors  known,  almost  equal  in 
this  respect  to  silver,  and  more  than  eight  times  a  better  con- 
ductor than  iron.  It  melts  at  a  temperature  a  little  above  that 
of  zinc,  between  zinc  and  silver.  In  its  chemical  qualities  it 
would  seem  to  take  an  intermediate  rank  between  whatjare 
termed  the  noble  metals  and  the  common  metals,  being,  as 
Deville  states,  one  of  the  most  unalterable  of  metals. 

"It  might  be  imagined  that  it  would  as  readily  reassume 
its  oxygen  as  it  parted  with  it  with  difficulty  when  in  its  state 
of  oxide.  This,  however,  is  not  the  case;  it  appears  to  be  as 
indifferent  to  oxygen  as  either  platinum  or  gold.  In  air  and 
in  oxygen  it  undergoes  no  sensible  alteration,  and  it  even  re- 
sists it  at  the  highest  temperature  which  Deville  could  produce 
in  a  cupelling  furnace,  a  temperature  higher  than  that  em- 
ployed in  assaying  gold.  Water  has  no  action,  according  to 
Deville,  on  aluminum,  neither  at  its  ordinary  temperature,  nor 
when  boiling,  nor  even  upon  the  metal  at  a  low  red  heat,  near 
its  melting-point.  J^ccording  to  Professor  Grace  Calvert,  this 
statement  must  be  received  with  some  degree  of  caution,  as  in 
experiments  he  has  made  he  considers  that  oxidation  does  take 
place  slowly  when  the  metal  is  immersed  in  water  for  any 
considerable  length  of  time.  It  is  not  affected  by  sulphur  or 
sulphuretted  hydrogen,  like  silver,  nor  is  it  acted  upon  to  any 
considerable  degree  by  any  of  the  oxy-acids  in  the  cold ;  nitric 
acid,  whether  strong  or  weak,  at  its  ordinary  temperature,  in 
no  way  affects  it,  though  when  boiling  it  acts  upon  it  slowly. 
Small  grains  of  aluminum,  plunged  in  sulphuric  acid  for  three 
months,  remained  apparently  unaltered.  The  vegetable  acids, 
such  as  acetic,  oxalic,  and.  tartaric  acids,  have  scarcely  any 
efiect  on  it  at  all.  The  true  solvent  of  the  metal  is  hydro- 
chloric acid,  which  attacks  it  rapidly.  It  appears  to  resemble 
tin  when  brought  into  contact  with  hydrochloric  acid  and  the 
chlorides.  Its  absolute  harmlessness  permits  of  its  being  em- 
ployed in  a  vast  number  of  cases  where  the  use  of  tin  would 


ALUMINUM.  85 

not  be  desirable  on  account  of  the  extreme  facility  with  which 
that  metal  is  dissolved  in  the  organic  acids. 

"Figuier,  in  his  scientific  Year  Book  for  1858,  just  pub- 
lished, states  that  the  caustic  alkalies,  potash,  and  soda,  and 
even  ammonia,  dissolve  aluminum  sensiljly.  He  also  states 
that  common  salt  and  acetic  acid  (vinegar),  especially  when 
mixed,  attack  and  dissolve  aluminum.  He  adds,  that  the  mix- 
ture of  salt  and  vinegar  for  seasoning  a  salad,  made  in  a  spoon 
of  aluminum,  feebly  but  inevitably  attacks  it. 

"All  these  points,  however,  deserve  to  be  inquired  into,  as 
there  seems  some  discrepancy  between  different  writers  on 
them." 

Alloys. — "  Aluminum,  like  iron,  does  not  unite  with  mer- 
cury, and  scarcely  at  all  with  lead.  It,  however,  forms  a 
variety  of  alloys  with  other  metals.  It  can  be  alloyed  with 
iron,  and  when  aluminum  becomes  clieaper,  it  will  be  curious 
to  see  what  effect  mixtures  of  this  metal  with  iron  will  have 
upon  its  quality,  whether  for  good  or  for  evil.  It  seems  to 
unite  readily  with  zinc,  and  these  have  been  found  to  give  the 
best  promise  as  solders  for  aluminum;  but,  unfortunately, 
when  melted,  neither  of  them  are  sufficiently  liquid,  and  does 
not  run  readily.  The  joints  will  not  bear  a  blow.  A  variety 
of  alloys  with  nickel  have  been  made,  and  that  consisting  of 
100  parts  of  aluminum  and  3  of  nickel,  is  found  to  work 
readily,  and  to  have  gained  hardness  and  rigidity,  as  compared 
with  the  pure  metal.  The  alloys,  however,  with  copper  are 
the  most  striking;  they  are  light  and  very  hard,  and  capable 
of  a  fine  polish.  In  the  same  degree  that  copper  adds  to  the 
hardness  of  aluminun),  so  does  the  latter,  when  used  in  small 
quantities,  give  hardness  to  copper,  without,  however,  injuring 
its  malleability.  It  renders  it  susceptible  of  a  fine  polish,  and, 
according  as  the  proportions  are  varied,  the  color  of  the  alloy 
becomes  deep  or  [tah  gold.  Alloys  of  copper  with  five  and 
ten  per  cent,  of  aluminum,  resemble  gold  perhaps  more  than 
any  other  metallic  alloy  hitherto  employed.  They  do  not  tar- 
nish sensibly  by  exposure  to  the  air.     xVluminum  can  be  de- 


86  MECHANICAL   DENTISTEY. 

posited  by  the  battery,  and  by  the  same  agent  it  can  be  gilt 
or  silvered." 

Some  attempts  have  been  made  to  render  aluminum  availa- 
ble as  a  base  for  artificial  teeth,  but  with  only  partial  success. 
When  in  the  form  of  plate,  no  suitable  solder  has  yet  been  dis- 
covered by  which  the  several  parts  of  a  dental  appliance  may 
be  securely  united  to  each  other ;  and  experiments  in  casting 
this  metal  have  practically  failed,  owing  to  its  extreme  lightness 
and  consequent  want  of  fluidity,  and  great  contraction.  More 
experience  in  its  proper  management,  and  a  further  acquaint- 
ance with  its  capabilities  in  yet  unknown  forms  of  combina- 
tion with  other  metals,  may  ultimately  demonstrate  its  general 
applicability  to  dental  purposes. 

At  the  present  time,  its  use  is  rarely  attempted  except  as  a 
base  in  connection  with  rubber  or  celluloid,  the  latter  sub- 
stances being  employed  as  a  means  of  attaching  teeth  by  a 
method  similar  to  that  described  in  another  place  when  gold  or 
silver  plate  is  used. 


COPPER.  87 


CHAPTER  IX. 

Copper,  Zixc,  Lead,  Tin,  Antimony,  and  Bismuth. 

COPPER. 

Copper  is  one  of  the  metals  most  anciently  known  ;  is  of  a 
brownish-red  color,  with  a  tinge  of  yellow ;  has  a  faint  but 
nauseous  and  disagreeable  taste,  and  imparts,  Avhen  exposed 
to  friction,  a  smell  somewhat  similar  to  its  taste.  Its  specific 
gravity  ranges  from  8.8  to  8.9.  It  is  both  malleable  and 
ductile,  but  excels  in  the  former  property,  finer  leaves  being 
obtained  from  it  than  wire.  It  is  inferior  to  iron  in  tenacity, 
but  surpasses  gold,  silver,  and  platinum  in  this  respect.  Cop- 
per melts  at  1996°  Fahrenheit. 

Alloys  of  Copper. — Copper  unites  readily  with  most  metals, 
forming  alloys  of  great  practical  value  in  the  arts,  but  which 
have  but  a  limited  application  in  dental  laboratory  processes. 
Many  of  these  alloys  are  curious  and  instructive  as  illustrating 
the  singular  and  unaccountable  influence  of  alloying  upon  the 
distinctive  properties  of  the  component  metals.  Copper  and 
tin,  for  example — the  former  of  which  is  highly  ductile,  and 
the  latter  equally  malleable — when  combined  in  the  propor- 
tion to  form  speculum  metal  (9  C  —  1  T),  forms  an  alloy  dis- 
tinguished for  its  extreme  brittleness,  with  a  surface  hardness 
almost  equal  to  steel.  By  increasing  the  quantity  of  tin  until 
the  compound  assumes  the  proportions  constituting  gun-metal 
(C  2  —  T  1),  the  alloy,  though  neither  malleable  or  ductile,  be- 
comes eminently  tough  and  rigid.  Other  prominent  examples 
might  be  given,  showing  how  completely  this  combining  influ- 
ence defies  all  calculations  in  regard  to  ultimate  results.  The 
following  summary  embraces  the  names  and  composition  of 
the  more  familiar  alloys  of  copi)er,  omitting,  as  unnecessary  in 
this  connection,  a  description  of  their  individul  properties. 


88  MECHANICAL,   DEJSTTISTEY. 

Alloys  of.  Copper  with  Zinc. — Brass  is  an  alloy  of  uncertain 
and  variable  composition,  consisting  usually,  however,  of  2  to 
5  parts  of  copper  and  one  of  zinc.  Brass  melts  at  1869° 
Fahr.  Prince's  metal,  and  its  allied  compounds.  Pinchbeck, 
Similor,  and  Ifanheim  gold,  consist  of  nearly  equal  parts  of 
copper  and  zinc.  Mosaic  gold  consists  of  100  parts  of  copper 
and  from  52  to  55  of  zinc.  Dutch  gold,  from  which  foil  of 
that  name  was  formerly  obtained,  is  formed  of  11  parts  of 
copper  with  2  of  zinc.  Bath  metal  is  composed  of  32  parts  of 
brass  and  9  of  zinc. 

Brass  solder  consists  of  2  parts  of  brass  and  1  of  zinc,  to 
which  a  little  tin  is  occasionally  added. 

Alloys  of  Copper  with  Tin. — Bell  metal  usually  consists  of 
100  parts  of  copper  with  from  60  to  63  parts  of  tin.  Cannon 
metal  is  compounded  of  90  parts  of  copper  with  10  of  tin. 
Cymbals  and  gongs  contain  100  parts  of  copper  and  25  of  tin. 
Speculum  metal  consists  of  two  parts  of  copper  and  1  of  tin. 

Copper  and  arsenic  form  a  white-colored  alloy,  and  in  the 
proportion  of  9  parts  of  copper  and  1  of  arsenic,  is  white, 
slightly  ductile,  and  is  denser  and  more  fusible  than  copper. 

Genuine  German  silver  is  composed  of  copper,  40.4 ;  Jiickel, 
31.6  ;  zinc,  25.4;  iron,  2,6  ;  but  the  proportions  of  the  metals 
of  this  alloy  differ  according  to  the  various  uses  to  which  this 
compound  is  applied. 

Chinese  pachfong  consists  of  5  parts  of  copper  alloyed  with 
7  parts  of  nickel  and  7  parts  of  zinc. 

A  very  useful  alloy,  employed  in  making  plummer  blocks, 
bushes,  and  steps  for  the  steel  and  iron  gudgeons  and  pivots  of 
machinery  to  run  in,  is  said  to  consist  of  90  parts  of  copper,  5 
of  zinc,  and  5  of  antimony. 

ZINC. 

Zinc  is  a  bluish-white  metal,  possessing  considerable  lustre 
when  broken  across.  The  commercial  variety  is  always  im- 
pure, containing  traces  of  iron,  lead,  cadmium,  arsenic,  carbon, 
etc.  It  does  not  easily  tarnish  in  dry  air,  but  soon  becomes 
dull  on  exposure  to  moisture.     In  the  condition  in  which  it 


LEAD.  89 

ordinarily  occurs  it  is  a  brittle  metal,  but  may  be  rendered 
malleable  by  annealing  it  at  certain  temperatures.  This 
change  in  its  condition  is  effected  by  subjecting  it  to  a  heat  of 
from  220°  to  300°,  at  which  temperature  it  may  be  rolled  into 
sheets,  and  retain  its  malleability  when  cold.  The  best  anneal- 
ing temperature  for  zinc  is  about  245°.  A  knowledge  of  this 
fact  will  enable  the  operator  to  avail  himself  of  the  advantages 
of  this  property  by  annealing  his  zinc  die,  by  which  its  liability 
to  crack  or  part  under  the  hammer  is  diminished. 

The  specific  gravity  of  zinc  varies  from  6.9  to  7.2.  It 
melts  at  about  773°,  and  Avhen  heated  much  above  this  point 
with  contact  of  air,  it  burns  with  a  brilliant  greenish-white 
flame,  while  woolly-looking  flocculi  rise  from  the  vessel  in 
which  it  is  being  heated  and  float  in  the  air. 

Zinc  has  been  long  and  almost  exclusively  employed  in  the 
formation  of  dies  used  in  swaging  metallic  plates  employed 
in  mounting  artificial  teeth,  and  experience  has  very  justly 
accorded  to  it  undisputed  pre-eminence  above  all  other  unal- 
loyed metals  for  the  purpose.  A  more  particular  account  of 
its  peculiar  fitness  for  dental  purposes  will  be  given  under  the 
head  of  Metallic  Dies  and  Counter-Dies. 

LEAD. 

Lead  has  a  grayish-blue  color,  with  a  bright  metallic  lustre 
when  melted  or  newly  cut,  but  it  soon  becomes  tarnished  and 
dull-colored  when  exposed  to  the  air.  The  specific  gravity  of 
commercial  lead,  which  is  usually  contaminated  with  other 
metals,  is  11.352.  It  fuses  at  612°.  Exposed  to  a  high  heat, 
it  absorbs  oxygen  rapidly,  forming  on  its  surface  a  gray  film 
of  protoxide  and  metallic  lead.  It  is  both  malleable  and  duc- 
tile, but  soft  and  perfectly  inelastic. 

Lead,  either  in  its  pure  state  or  when  alloyed  with  certain 
other  metals,  serves  important  purposes  in  the  laboratory.  In 
its  simple  or  uncombined  state  it  is  useful  only  in  forming 
counter-dies.  Alloyed  with  antimony  in  the  proportion  of 
from  ^  to  J  of  the  latter,  with  the  addition  sometimes  of  very 


90  MECHANICAL   DENTISTRY. 

small  portions  of  copper,  tin,  and  bismuth,  it  forms  different 
grades  of  type-metal,  which  is  harder  than  lead,  and  very 
brittle,  and  is  sometimes  used  for  dies ;  and  sometimes,  though 
very  rarely,  for  counter-dies.  When  used  as  a  counter  to  a 
zinc  die,  it  is  improved  for  the  purpose  by  adding  to  it  an 
equal  quantity  of  lead ;  it  may  also  be  used  in  the  form  of  a 
die  in  connection  with  a  lead  counter  after  rough  stamping 
with  zinc. 

The  alloy  known  as  Rose's  fusible  metal  is  composed  of  2 
parts  of  bismuth  to  1  of  lead,  and  1  of  tin,  and  melts  at  about 
200°.  A  still  more  fusible  alloy  is  composed  of  lead  3  parts, 
tin  2  parts,  and  bismuth  5  parts,  which  fuses  at  197°.  There 
are  other  alloys  of  lead,  to  be  mentioned  hereafter,  melting  at 
from  200°  to  440°,  which  may  be  advantageously  employed 
in  forming  dies  to  be  used  after  zinc,  where  the  latter,  from  its 
greater  shrinkage,  fails  to  bring  the  plate  into  accurate  adap- 
tation to  the  mouth. 

Soft  solder  is  an  alloy  composed  of  lead  and  tin  in  the  pro- 
portion of  two  parts  of  the  former  to  one  of  the  latter. 

TIN. 

Tin  is  a  brilliant,  silver-white  metal,  the  lustre  of  which  is 
not  sensibly  aifected  by  exposure  to  the  air,  but  is  easily  oxi- 
dized by  heat.  It  has  a  slightly  disagreeable  taste,  and  emits, 
when  rubbed,  a  peculiar  odor.  It  is  soft,  inelastic,  and,  when 
bent,  emits  a  peculiar  cracking  sound  called  the  creaking  of 
tin.  It  is  inferior  in  tenacity  and  ductility,  but  is  very  mal- 
leable, and  may  be  beaten  into  leaves  the  2¥o¥  ^^  ^^  ^^^^  ^^ 
thickness ;  ordinary  tin  foil  being  about  y  ^^q-^  of  an  inch 
thick.  It  fuses  at  442° ;  boils  at  a  white  heat,  and  burns 
with  a  blue  flame  to  binoxide. 

The  more  common  alloys  of  tin  with  other  metals  have 
already  been  noticed.  It  was  at  one  time  used  as  a  base  for 
artificial  teeth ;  and,  more  recently,  it  has  been  introduced  as 
a  component  of  "  cheoplastic  "  metal,  a  compound  used  for  the 
same  purpose.      In  its  pure  state,  it  is  sometimes  used  for 


BISMUTH.  91 

counter-dies,  and  occasionally  for  dies.  When  employed  for 
the  latter  purpose  in  connection  with  a  lead  counter,  the  latter 
should  not  be  obtained  directly  from  the  die,  as  the  high  tem- 
perature of  melted  lead  would  produce,  when  poured  upon  tin, 
partial  fusion  of  the  latter  and  consequent  adhesion  of  the  two 
pieces.  When  tin  is  used  in  the  formation  of  a  die,  therefore, 
either  a  counter  previously  obtained  from  a  zinc  die  should  be 
used,  or  the  "dipping"  method  employed,  by  which  the 
counter-die  is  first  obtained  from  the  plaster  model,  and  a  die 
from  the  counter. 

ANTIMONY. 

Antimony  is  of  a  silver-white  color,  with  a  tinge  of  blue,  a 
lamellar  texture,  and  a  crystalline  fracture.  It  is  brittle  and 
easily  pulverized.  The  specific  gravity  of  the  purest  variety 
is  6.715.  It  fuses  at  about  810°,  and  when  heated  at  the 
blowpipe,  it  melts  with  great  readiness,  and  diffuses  white 
vapors,  possessing  somewhat  of  a  garlic  smell. 

Antimony  enters  as  an  ingredient  into  the  composition  of 
type  and  stereotype  metal,  music  plates,  and  Britannia  metal. 
It  is  also  a'  component  of  certain  fusible  alloys  analogous  to 
those  already  mentioned  under  the  head  of  lead,  and  which,  in 
the  form  of  a  die,  are  sometimes  used  on  account  of  their 
slight  degree  of  shrinkage. 

BISMUTH. 

Bismuth  is  a  white-colored  metal  resembling,  in  some  de- 
gree, antimony.  It  is  soft,  but  so  brittle  as  to  be  easily  pul- 
verized. Its  specific  gravity  is  9.83,  which  may  be  increased 
somewhat  by  hammering.  It  melts  at  480°  Fah.,  and  may 
be  cooled  six  or  seven  degrees  below  this  point  without  fixing; 
but  the  moment  it  begins  to  solidify  the  temperature  rises  to 
480°,  and  continues  stationary  till  the  whole  mass  is  congealed. 
When  the  temperature  of  the  metal  is  raised  from  32°  to  212°  ' 
it  expands  ^i^  in  length. 

Bismuth  has  the  property,  in  a  high  degree,  of  increasing 
the  fusibility  of  the  metals  with  which  it  is  incorporated,  and 


92  .  MECHANICAL   DENTISTRY. 

is  a  common  ingredient  of  the  more  fusible  alloys,  some  of 
which  melt  in  boiling  water.  One  part  of  bismuth  with  24 
of  tin  is  malleable,  but  the  alloy  of  these  metals  becomes 
brittle  by  the  addition  of  more  bismuth.  Bismuth  unites 
readily  with  antimony,  and  in  the  proportion  of  one  part  or 
more  of  the  former  to  two  of  the  latter,  it  expands  in  the  act 
of  cooling. 

There  are  many  other  metals  and  alloys  besides  those 
already  enumerated,  but  which  have  not  been  particularly 
described  on  account  of  their  inutility  in  the  laboratory  for 
dental  purposes.  Among  these  may  be  mentioned  iron,  brass, 
bronze,  etc.,  which  are  only  employed  for  auxiliary  purposes, 
and  are  both  inconvenient  and  impracticable  for  dies  on  account 
of  their  infusible  nature  and  consequent  contraction ;  nickel, 
on  account,  also,  of  its  extreme  infusibility  and  its  tendency  to 
render  the  alloy,  of  which  it  is  a  component,  less  fusible ; 
sodium,  on  account  of  the  changes  produced  on  it  by  exposure 
to  the  air ;  potassium,  on  account  of  its  extreme  sensitiveness 
to  the  influence  of  low  temperature,  being  semi-fluid  at  60° 
Fah.,  nearly  liquid  at  92°,  and  entirely  so  at  120°  ;  arsenic, 
because  it  volatilizes  before  fusing;  cadmium,  with  no  ad- 
vantages above  tin,  on  account  of  its  scarcity  and  costliness ; 
etc. 


GENERAL  PROPERTIES  OF  ALLOYS.         93 


CHAPTER   X. 

General  Properties   of  Alloys,  and  their  Treat- 
ment AND  Behavior  in  the  Process  of 
Compounding. 

All  alloys  possess  metallic  lustre,  are  opaque,  conduct  heat 
and  electricity,  and,  in  a  greater  or  less  degree,  are  ductile 
malleable,  elastic,  and  sonorous.  Some  alloys,  as  brass  and 
gong-metal,  are  usually  malleable  in  the  cold,  and  brittle  when 
hot. 

Metals  sometimes  unite  in  atomic  ratios,  forming  compounds 
of  definite  or  equivalent  proportions  of  the  component  metals, 
as  certain  alloys  of  copper  and  zinc,  gold  and  copper,  gold 
and  silver,  mercurial  alloys,  etc.,  while,  on  the  other  hand, 
many  are  formed  in  all  proportions,  like  mixtures  of  salt  and 
water. 

Metals  differ  in  respect  to  their  affinity  for  each  other,  and 
do  not,  therefore,  alloy  with  equal  focility ;  thus  it  is  difficult 
to  unite  silver  and  iron,  but  the  former  combines  readily  with 
gold,  copper,  or  lead. 

The  ductility  of  an  alloy  is,  in  general,  less  than  that  of  its 
constituent  metals,  and  this  diffiirence  is,  in  some  instances, 
reraarkaljly  prominent,  as  in  the  case  of  certain  alloys  of  cop- 
per and  tin,  already  mentioned. 

An  alloy  is  generally  harder  than  the  mean  hardness  of  its 
components,  a  property  which,  when  taken  in  connection  with 
their  increased  fusibility,  gives  to  alloys  peculiar  value  in  the 
formation  of  dies  for  stamping  purposes.  To  the  rule  stated, 
amalgams,  or  mercurial  alloys,  are  cited  as  exceptions. 

The  density  of  an  alloy  varies  with  the  particular  metals 
composing  it,  being  generally  either  greater  or  less  than  the 
mean  density  of  its  several  components. 


94  MECHANICAL    DENTISTRY. 

It  is  impossible  to  predict  with  certainty  the  melting-point 
of  an  alloy  from  that  of  its  separate  constituents,  but,  generally, 
the  fusibility  of  the  alloy  is  increased,  sometimes  in  a  most 
remarkable  degree.  The  alloy  of  5  parts  of  bismuth,  3  of 
lead,  and  2  of  tin  is  a  striking  example  of  this  fact,  this  com- 
pound melting  at  197°,  while  the  mean  melting-point  of  its 
constituents  is  514°.  Silver  solder  is  also  a  familiar  illustra- 
tion of  the  influence  of  alloying  on  the  fusibility  of  metals, 
copper  melting  at  1996°,  and  silver  at  1873°,  when  com- 
bined, fuse  at  a  heat  much  below  that  required  to  melt  silver, 
the  more  fusible  component  of  the  alloy.  Again,  iron,  which 
melts  at  a  little  less  than  3000°,  acquires  almost  the  fusibility 
of  gold  when  alloyed  with  the  latter.  Examples  might  be 
multiplied,  but  it  will  be  sufficient  to  add  that,  in  general, 
metallic  alloys  melt  at  a  lower  heat  than  is  required  to  fuse  the 
most  refractory  or  infusible  component,  and  sometimes  than 
the  most  fusible  ingredient. 

The  color  of  an  alloy  cannot,  in  general,  be  inferred  from 
that  of  its  component  metals  ;  thus  it  would  be  conjectured 
that  copper  would  be  rendered  very  much  paler  by  adding  to 
it  zinc  in  considerable  quantities,  but  the  fallacy  of  such  an  in- 
ference is  at  once  shown  by  an  examination  of  some  of  the  rich- 
looking  gold-colored  varieties  of  brass,  as  Prince's  metal, 
pinchbeck,  and  similor,  composed  each  of  nearly  equal  parts 
of  copper  and  zinc ;  and  manheim  gold,  compounded  of  3  parts 
copper  and  1  of  zinc. 

The  affinity  of  an  alloy  for  oxygen  is  greater  than  that  of 
the  separate  metals,  a  phenomenon  that  is  ascribed  by  Ure  to 
the  increase  of  affinity  for  oxygen  which  results  from  the  ten- 
dency of  one  of  the  oxides  to  combine  with  the  other;  by  others 
it  is  attributed  to  galvanic  action.  According  to  Faraday,  100 
parts  of  steel,  alloyed  with  one  of  platinum,  is  dissolved  with 
eflPervescence,  in  dilute  sulphuric  acid  too  weak  to  act  with 
perceptible  energy  on  common  steel.  It  is  offered,  in  explana- 
tion of  this  fact,  that  the  steel  is  rendered  positive  by  the  pres- 
ence of  platinum.     A  similar  illustration  is  afforded  by  the 


GENERAL  PROPERTIES  OF  ALLOYS.  95 

action  of  dilute  acid  on  commercial  zinc,  which  is  usually  an 
alloy  of  zinc  with  other  metals. 

The  action  of  air  is,  in  general,  less  on  alloys  than  on  the 
separate  metals  composing  them.  To  this,  however,  there 
are  exceptions,  as  the  alloy  of  3  parts  of  lead  and  1  of 
tin,  which,  when  heated  to  redness,  burns  briskly  into  a  red 
oxide. 

Some  points  of  practical  interest  suggest  themselves  in  con- 
nection with  the  behavior  and  proper  management  of  alloys  in 
the  process  of  compounding. 

As  metallic  alloys  can  only  be  formed  by  fusion,  and  as  the 
affinity  of  the  metals  composing  them  for  oxygen  is  greatly  in- 
creased by  heat,  especially  those  denominated  base,  it  is 
important  that  this  tendency,  which  is  incompatible  with  the 
proportional  accurateness  of  the  compound,  should  be,  as  far  as 
practicable,  guarded  against.  Hence,  various  substances  hav- 
ing a  greater  affinity  for  oxygen  than  the  metals  to  be  united, 
as  oil  or  grease,  rosin,  powdered  charcoal,  etc.,  are  generally 
added,  coating  the  surface  of  the  liquid  metals,  and  which,  by 
affijrding  a  protective  covering,  preserves,  with  little  change, 
the  proportions  of  the  alloy. 

Some  difficulty  is  occasionally  experienced  in  obtaining  a 
perfectly  uniform  alloy  on  account  of  the  different  specific 
gravities  of  the  metals  composing  it — each  metal  assuming  the 
level  due  to  its  density.  This  partial  separation  is  common  to 
gold  and  silver,  provided  they  have  not  been  adequately 
stirred  before  pouring.  This  result  is  not  so  likely  to  occur 
when  the  metals  employed  are  in  small  quantities  and  are  sud- 
denly cooled,  but  when  used  in  considerable  masses  and  allowed 
to  cool  slowly,  it  is  much  favored  by  permitting  the  metals  to 
fix  themselves  in  the  ofder  of  their  separate  densities.  Hence, 
whenever  a  notable  difference  in  the  specific  gravity  of  the 
metals  exists,  the  fused  mass  should  be  briskly  stirred  imme- 
diately before  the  instant  of  pouring  it,  and  should  be  made  to 
solidify  quickly.  If  uniformity  be  not  obtained  in  this  man- 
ner, it  will  be  necessary  to  rcmelt,  and  repeat  the  process,  if 
necessary,  until  the  alloy  is  rendered  sufficiently  homogeneous. 


96  MECHANICAL    DENTISTRY. 

In  alloying  three  or  more  metals  diiFering  greatly  in  fusi- 
bility, or  that  have  but  little  affinity  for  each  other,  it  is  better 
to  first  unite  those  which  most  readily  combine,  and,  afterward, 
these  with  the  remaining  metal  or  metals.  If,  for  example,  it 
is  desired  to  unite  a  small  quantity  of  lead  with  brass  or  bronze, 
some  difficulty  would  be  experienced  in  forming  the  alloy  by 
direct  incorporation  of  the  metals,  but  union  could  be  readily 
effected  by  first  melting  the  lead  with  zinc  or  tin,  and  then 
adding  the  melted  copper. 


PART  SECOND. 

AKTIFICIAL  DENTURES. 

Before  considering  particularly  the  distinct  and  sj^ecial 
methods  employed  in  the  construction  of  artificial  dentures, 
such  preliminary  processes  as  are  common,  in  some  degree,  to 
all,  will,  for  the  sake  of  convenient  arrangement,  and  the 
avoidance  of  unnecessary  repetition  hereafter,  be  first  consid- 
ered. These  processes  relate:  1.  To  the  treatment  of  the 
mouth  preparatory  to  the  insertion  of  artificial  teeth.  2.  The 
manner  of  obtaining  impressions  of  the  mouth.  3.  The 
manner  of  procuring  and  forming  plaster  models  of  tlie  mouth. 
4.  Metallic  dies  and  counter-dies. 


CHAPTER    I. 


Treatment  of  the  Mouth  preparatory  to  the  Inser- 
tion OF  Artificial  Dentures. 

It  rarely  occurs  that  all  the  structures  of  the  mouth  arc  in 
such  condition  as  will  render  it  proper  to  insert  an  artificial 
appliance  without  some  pixiparatory  treatment.  This  impor- 
tant requirement  cannot,  in  any  material  respect,  be  disre- 
garded by  the  practitioner  without  endangering  the  utility 
and  permanence  of  the  substitute,  and  inflicting  upon  the 
patient  a  train  of  consequences  alike  distressing  and  perni- 
cious. Every  experienced  dentist  is  familiar  with  the  fact 
that  an  artificial  substitute  resting  upon  diseased  roots  of 
teeth  and  impinging  continually  upon  gums  ah'cady  irritable 

7 


98  MECHANICAL   DENTISTRY. 

and  inflamed^  soon  becomes  a  source  not  only  of  annoyance 
and  discomfort  to  the  patient,  but  is  rendered,  in  a  great  de- 
gree, inefficient  in  the  performance  of  some  of  its  more  impor- 
tant offices.  There  is,  besides,  a  perpetual  and  cumulative 
aggravation  of  the  morbid  conditions,  and,  sooner  or  later, 
irretrievable  destruction  of  the  remaining  natural  organs  will 
be  induced.  These  consequences  cannot  be  wholly  averted  by 
the  most  skilful  manipulation,  but  they  may  be  greatly  mag- 
nified by  a  defective  execution  of  the  work  or  by  a  faulty 
adaptation  of  the  appliance  to  the  parts  in  the  mouth. 

Patients  not  unfrequently  attempt,  by  every  artifice  or  pre- 
text that  caprice  or  timidity  may  suggest,  to  persuade  the 
operator  to  violate  his  own  clear  convictions  of  duty,  but,  un- 
less under  circumstances  of  peculiar  exigency,  he  should  be 
careful  to  guard  himself  against  the  imputation  of  incom- 
petency or  bad  faith  by  being  peremptory  and  unyielding  in 
his  demands  upon  the  patient  to  submit  to  the  necessities  and 
just  requirements  of  the  case,  and  no  ordinary  circumstance 
should  influence  him  in  opposition  to  his  better  informed 
judgment. 

The  conditions,  usually  met  with,  to  which  it  will  be  neces- 
sary to  direct  attention  in  the  treatment  of  the  mouth,  are,  the 
presence  of  useless  and  diseased  remains  of  teeth;  accumula- 
tions of  tartar ;  diseased  states  of  the  gums  and  mucous  mem- 
brane ;  and  caries. 

Useless  and  Diseased  Remains  of  Teeth. — It  may  be  stated, 
as  a  general  rule  of  practice,  that .  all  the  remaining  natural 
teeth  that  are  not  susceptible  of  being  restored  to  a  state  of 
comparative  health  and  usefulness,  should  be  removed  before 
inserting  an  artificial  substitute.  Especially  should  this  course 
be  pursued  whenever  the  remaining  roots  are  found  partially 
or  wholly  necrosed,  and  the  peridental  membranes  and  sur- 
rounding tissues  inflamed  and  suppurating.  Such  should  be 
extracted  if  for  no  other  reason  than  that  they  are  offensive  in 
the  mouth,  and  tend,  in  a  greater  or  less  degree,  to  compromise 
the  general  health. 

In  respect  to  the  utility,  comfort,  and  permanence  of  a 


TREATMENT   OF    THE    MOUTH.  99 

dental  appliance,  the  expediency  of  removing  the  roots  of  teeth 
prior  to  the  introduction  of  the  former,  is  apparent.  If  a 
dental  substitute  is  adapted  with  necessary  accuracy  to  all  the 
parts  which  it  covers,  it  will  be  plainly  seen  that  the  forces 
applied  to  the  base  at  every  occlusion  of  the  jaws  in  the  act  of 
mastication,  instead  of  being  equalized  or  diffused,  will  be  ex- 
pended mainly  on  the  roots,  inasmuch  as  they  afford  so  many 
fixed  points  of  resistance,  whilst  the  adjacent  soft  tissues,  yield- 
ing to  the  pressure,  permit  the  artificial  piece  to  bear  with  un- 
due and  unequal  force  upon  the  former.  The  consequences  of 
this  action  are  inevitably  pernicious.  In  a  comparatively  short 
time,  inflammation  and  suppuration  are  induced  about  the 
roots,  which  ultimately  become  loosened  and  painfully  sensitive 
to  the  slightest  pressure;  the  secretions  of  the  mouth,  becom- 
ing more  and  more  acrimonious,  act  persistently  and  with  in- 
creasing energy  on  oxidable  materials  present  in  the  mouth, 
as  well  as  upon  the  remaining  natural  teeth,  inducing  rapid 
and  general  decay ;  contiguous  parts,  through  their  immediate 
connection  or  sympathetic  relations  with  the  structures  of  the 
mouth,  respond  to  the  local  disturbances,  and  the  case,  in  time, 
becomes  complicated  with  those  various  distressing  maladies 
about  the  head  and  face  so  commonly  associated  with  diseased 
conditions  of  the  buccal  cavity.  At  last,  the  patient,  no  longer 
able  to  endure  the  offensiveness  and  distress  arising  from  the 
presence  of  the  substitute  in  the  mouth,  or  to  properly  masti- 
cate his  food,  is  compelled  to  have  the  offending  organs  re- 
moved. The  absorption  of  the  gums  and  processes  which 
follow  this  operation,  and  the  corresponding  changes  which 
occur  therefrom  in  the  form  of  the  alveolar  ridge,  make  it  im- 
perative in  all  cases  either  to  reconstruct  the  same  piece  or  to 
supply  the  ])atient  with  an  entirely  new  substitute ;  whereas,  if 
due  regard  is  had  to  the  proper  preparation  of  the  mouth  in 
the  first  instance,  the  patient  may  be  spared  such  inflictions, 
and  the  o])erator  the  discredit  which  almost  invariably  attaches 
to  the  neglect  of  the  measures  recommended. 

An  additional  reason  why  roots  of  teeth  should  be  extracted 
Is,  that  their  presence  prevents,  in  some  degree,  an  accurate 


100  MECHANICAL   DENTISTEY. 

and  uniform  adaptation  of  the  appliance  to  all  the  parts  on 
which  it  is  designed  to  rest,  and  this  is  particularly  true  of 
those  cases  where  atmospheric  pressure  is  made  available  in 
the  retention  of  the  substitute.  Any  condition  of  the  mouth 
that  prominently  modifies  the  natural  and  uniform  pliancy  of 
the  soft  parts  will,  just  to  that  extent,  weaken  the  attach- 
ment of  the  plate.  This  fact  is  made  obvious  when  we  reflect 
that  it  is  only  the  soft  and  yielding  condition  of  the  mucous 
membrane  and  gums  that  permits  the  adhesion  of  the  artificial 
appliance  for  a  single  moment  by  atmospheric  pressure ;  for  it 
will  be  readily  comprehended  that,  if  the  tissues  on  which  it 
rests  were  as  hard  and  unyielding  as  bone,  a  dental  substitute, 
though  it  were  moulded  directly  to  the  parts,  would  not  be 
sustained  for  an  instant  by  the  external  pressure  of  the  air. 

The  retention  of  every  root  that  may,  by  treatment  or  other- 
wise, be  secured  in  good  condition,  has  been  insisted  on  by  a 
few  in  the  profession,  on  the  ground  that  they  aiford  a  fixed 
and  permanent  basis  for  the  dental  appliance,  and  preserve, 
without  change,  the  customary  fulness  and  contour  of  the 
mouth.  Individual  instances  doubtless  occur  that  render  this 
course  admissible,  but  as  a  rule  of  practice,  it  is  exposed,  though 
in  a  less  degree  perhaps,  to  the  same  objections  which  have 
been  adverted  to  in  connection  with  diseased  roots.  However 
carefully  or  skilfully  such  roots  may  be  treated  and  prepared, 
or  the  substitute  applied,  entire  success  and  permanent  benefit 
to  the  patient  cannot  be  reasonably  anticipated.  It  rarely  hap- 
pens that  the  roots  of  teeth,  whose  crowns  have  been  destroyed 
by  caries  or  accident,  are  found  without  having  suffered,  at 
some  time  and  in  some  degree,  from  disease  of  the  investing 
membranes  and  surrounding  structures,  and  although  these 
conditions  may  have  apparently  subsided,  or  may  have  been 
temporarily  subdued  by  .  treatment,  yet  observation  of  such 
cases  leads  to  the  conclusion  that,  however  free  from  indica- 
tions of  active  disease  they  may  appear  at  the  time,  the  latent 
predisposition  favoring  a  recurrence  of  the  morbid  action 
usually  exists  in  such  cases,  and  it  will  require  no  greater  prov- 
ocation than  the  continued  and  unequal  action  of  an  artificial 


TREATMENT  OF  THE  MOUTH.  101 

fixture  on  them  to  awaken  this  predisposition  into  active  de- 
velopment. 

From  the  views  here  expressed,  we  are  convinced  that  as  a 
principle  of  practice,  the  roots  of  teeth,  however  apparently 
free  from  disease,  should  be  extracted  in  the  first  instance. 
There  are,  nevertheless,  circumstances  which  clearly  justify  a 
departure  from  the  rule  we  have  endeavored  to  enforce;  as  in 
the  process  of  engrafting  an  artificial  crown  upon  a  well-con- 
ditioned root ;  or  supplying  the  loss  of  one  or  more  of  the  front 
teeth  by  attaching  the  artificial  organs  to  a  plate  and  fixing  the 
latter  in  the  mouth  by  pivoting  to  one  or  more  of  the  natural 
roots.  Either  of  these  methods  may,  under  certain  circum- 
stances and  within  certain  limitations,  be  preferable  to  extract- 
ing the  roots  of  such  teeth  and  supplying  the  vacuities  by  other 
means. 

JRemoral  of  Salivary  Cak-idiis  or  Tartar: — The  deposits  of 
tartar  which  so  frequently  collect  at  the  necks  of  the  teeth  and 
under  the  free  margins  of  the  gum,  not  only  promote  inflam- 
mation and  absorption  of  the  investing  membrane  and  contigu- 
ous soft  ])arts,  but  involve,  by  degrees,  the  alveolar  processes 
in  the  destructive  action ;  so  that  teeth  originally  firm  become 
loosened  in  their  sockets,  and  thus,  in  their  turn,  become  addi- 
tional sources  of  diseased  action  in  the  surrounding  structures. 
Hence  it  becomes  absolutely  necessary,  as  it  relates  to  the  gen- 
eral health  of  the  mouth,  to  thoroughly  remove,  with  suitable 
instruments,  all  traces  of  this  concretion  from  the  teeth. 

If  any  considerable  number  of  the  teeth  are  found  coated 
with  tartar,  and  it  is  deposited  in  large  quantities,  it  will  be 
impracticable,  as  a  general  thing,  to  remove  thoroughly  all 
remains  of  it  at  a  single  sitting.  The  operation  should  be 
repeated,  therefore,  from  time  to  time,  until  every  portion  of 
it  is  completely  separated  from  the  teetii ;  the  latter  should 
then  be  well  polished  with  suitably  shaped  burnishers,  and 
the  gums,  if  highly  inflamed  and  turgid,  may  be  either  freely 
scarified  at  those  points  where  they  dij)  between  the  teeth,  or 
clejmsed  and  treated  with  appropriate  detergent  and  remedial 
agents. 


102  MECHANICAL    DENTISTRY. 

Diseased  Conditions  of  the  3'Iucous  Membrane  and  Gums. — 
It  will  seldom  be  necessary  to  institute  treatment  for  the  reduc- 
tion of  inflammation  and  ulceration  of  the  soft  tissues  of  the 
mouth  after  the  removal  of  diseased  roots  and  tartar,  inasmuch 
as  these  conditions  being  generally  provoked  by,  and  associated 
with,  the  latter,  will  spontaneously  subside  with  the  removal 
of  the  exciting  causes.  If,  however,  there  are  other  morbid 
conditions  of  the  soft  tissues  or  osseous  structures  of  the  mouth 
not  immediately  arising  from  the  presence  of  diseased  roots  and 
tartar,  they  should  be  treated  in  accordance  with  the  particular 
pathological  conditions  present. 

Caries  or  Decay  of  the  Remaining  Teeth. — In  order  that  all 
the  teeth  which  it  is  deemed  advisable  to  retain  in  the  mouth 
may  be  permanently  preserved,  it  will  be  necessary  to  fill,  or 
otherwise  treat,  such  as  may  be  affected  by  caries.  This  opera- 
tion will  be  attended  with  more  satisfactory  results  and  be 
accompanied  with  less  pain  to  the  patient,  and  diminished  risk 
of  failure,  when  performed  after  the  removal  of  the  roots  of 
teeth  and  tartar,  and  the  restoration  of  diseased  conditions  of 
the  mouth  to  health,  as,  in  this  case,  there  will  be  less  irrita- 
bility of  the  general  system,  and  reduced  sensitiveness  of  the 
teeth  operated  on. 

Siirgieal  Treatment  of  the  Moidh  after  the  Extraction  of 
Teeth. — In  the  preparation  of  the  mouth  for  entire  sets  of  arti- 
ficial teeth,  it  frequently  becomes  necessary  to  extract  the  re- 
mains of  all  or  nearly  all  of  the  teeth  of  one  or  both  jaws.  In 
such  cases,  the  ridge  is  left  ragged  and  broken,  with  flaps  of 
gum  lying  in  loose  folds  along  the  border,  and  the  exposed 
margins  of  the  alveolar  processes  projecting  from  underneath. 
These  parts,  if  left  in  this  condition,  will  be  productive  of  more 
or  less  inconvenience  to  the  patient ;  for  as  the  gums  close  over 
and  contract  upon  the  cutting  edges  of  the  processes,  irritation 
and  inflammation  will  be  induced  at  those  points  where  they 
are  most  prominent.  Immediately  after  the  extraction  of  the 
teeth,  therefore,  any  flaps  of  gum  hanging  loosely  around  the 
sockets  should  be  clipped  off,  and  sharp  and  protruding  portions 
of  processes  cut  away  with  excising  forceps.     If^  in  the  course 


TREATMENT  OF  THE  MOUTH.  103 

of  a  few  weeks,  prominences  still  remain,  over  which  the  mucous 
membrane  is  stretched  and  irritated  or  inflamed,  as  is  more  fre- 
quently the  case  around  the  sockets  of  the  cuspidati,  the  mem- 
brane should  be  divided  over  such  points  with  a  lancet,  and  the 
sharp  points  of  bone  underneath  broken  down  with  suitable  cut- 
ting instruments. 

Time  Necessary  to  Elapse  after  the  Extraction  of  Teeth  before 
Inserting  Artificial  Dentures. — The  time  that  should  elapse  after 
extracting  the  natural  teeth,  before  replacing  them  with  arti- 
ficial substitutes,  will  depend  upon  various  circumstances.  If 
the  appliance  is  only  intended  to  meet  the  wants  of  the  indi- 
vidual until  all  the  changes  effected  by  absorption  of  the  gums 
and  processes  are  fully  completed,  it  may  be  inserted  in  from 
one  to  three  weeks,  depending  somewhat  upon  the  number  of 
teeth  extracted,  the  extent  of  the  injuries  unavoidably  inflicted 
upon  the  parts,  and  the  virulence  of  the  diseased  action  present 
in  the  structures  of  the  mouth  at  the  time  of  the  operation.  If 
there  are  no  unusual  complications,  and  the  space  or  spaces  to 
be  supplied  are  such  as  are  made  by  the  loss  of  only  one  or  two 
teeth  at  intervals,  the  parts  quickly  assume  their  normal  con- 
dition, and  the  piece  to  be  temporarily  worn  may  be  applied 
within  a  few  days.  If,  however,  a  greater  number  or  all  of 
the  teeth  have  been  removed,  more  or  less  inflammation  and 
tenderness  will  be  present  for  from  ten  days  to  two  or  three 
weeks,  and  which  will  render  the  wearing  of  an  artificial  piece 
uncomfortable  to  the  patient,  and  in  some  degree  mischievous, 
by  aggravating  the  morbid  conditions  already  existing.  An- 
other objection  to  the  too  early  introduction  of  artificial  sub- 
stitutes into  the  mouth  arises  from  the  fact  that  the  changes 
wliicii  occur  in  the  ridge  are  much  more  rapid  within  the  first 
few  weeks  after  the  extraction  of  the  teeth  than  at  any  subse- 
quent period,  so  that  the  plate,  if  inserted  immediately  or 
within  a  few  days  after  such  operation,  will  soon  lose  its  bear- 
ing upon  the  ridge  and  become  inefficient  for  masticating  pur- 
poses, or  may  even  fiiil  to  be  retained  in  the  mouth  without 
much  annoyance  to  the  patient.  Two  or  more  weeks,  therefore, 
should  elapse  before  applying  the  substitute.    In  the  meantime, 


104  MECHANICAL    DENTISTRY. 

the  patient  should  be  seen  frequently,  and  such  medical  or 
surgical  treatment  adopted  from  time  to  time  as  the  case  may 
demand. 

The  time  occupied  in  the  compldion  of  those  changes  which 
occur  in  the  alveolar  border  after  the  extraction  of  all  or  any 
considerable  number  of  the  teeth,  cannot  be  definitely  stated, 
but  will  range  from  five  to  eighteen  months  or  more,  accord- 
ing to  the  amount  of  superfluous  structures  to  be  removed,  the 
density  of  the  osseous  tissues,  and  the  functional  activity  of  the 
absorbents.  In  all  cases,  ample  time  should  be  permitted  to 
elapse  in  order  that  no  appreciable  change  in  the  form  of  the 
parts  may  take  place  after  the  appliance  has  been  permanently 
adjusted; 


OBTAINING  IMPRESSIONS   OF   THE   MOUTH.  105 


CHAPTER   II, 

Materials  and  Methods  Employed  in  Obtaining 
Impressions  of  the  Mouth. 

In  the  process  of  constructing  a  dental  substitute,  it  is  of 
the  first  importance  that  as  accurate  an  impression  as  possible 
should  be  obtained  of  all  those  parts  of  the  mouth  with  which 
the  appliance  is  in  any  way  connected.  If  this  important  pre- 
liminary step  is,  in  any  essential  respect,  imperfectly  performed, 
the  ultimate  utility  of  the  artificial  fixture  will  either  be  greatly 
impaired  or  wholly  destroyed,  notwithstanding  all  the  subse- 
quent manipulations  may  be  most  carefully  and  skilfully  per- 
formed. The  operator,  therefore,  should  avail  himself  of  every 
appliance  and  facility  that  will  enable  him  to  attain,  in  this 
respect,  the  most  perfect  results. 

The  materials  ordinarily  employed  for  this  purpose  are, 
wax;  combinations  of  wax  and  paraffin  and  gutta-percha; 
modelling  composition;  gutta-percha;  and  plaster  of  Paris. 

Wax. — There  are  two  varieties  of  this  substance  in  common 
use,  the  yellow  and  tchite  wax.  The  yellow  variety  is  es- 
teemed preferable  to  the  white  on  account  of  its  superior  tough- 
ness ;  the  latter  being,  to  some  extent,  disintegrated,  or  ren- 
dered less  tenacious  in  the  process  of  bleaching,  but  is  fre- 
quently used  and  is  preferred  by  many  on  account  of  its  color. 
The  more  desirable  properties  of  the  yellow  wax  are  often  im- 
paired by  the  admixture  with  it  of  tallow,  with  which  it  is, 
for  mercenary  purposes,  frequently  contaminated.  The  pres- 
ence of  tallow  may  be  detected  by  its  characteristic  odor,  and  by 
the  whitish  or  pale-yellow  color  it  imparts  to  the  wax,  which 
in  its  pure  state,  is  of  a  deep,  bright  straw-color. 

Wax  used  for  impressions  should  always  be  kept  in  con- 
venient form  for  immediate  use,  and  may  be  prepared  either 


106  MECHANICAL   DENTISTRY. 

by  warming  it  until  sufficiently  soft  and  then  rolling;  or  press- 
ing it  into  thin  sheets;  or  having  melted  it  in  a  properly 
formed  vessel,  immerse  in  it  a  strip  of  thin  board,  previously 
moistened,  and  withdraw,  quickly ;  this  is  repeated  as  the  suc- 
cessive layers  cool,  until  a  coating  of  sufficient  thickness  is  ob- 
tained. The  latter  is  a  convenient  method  of  obtaining  sheets 
of  wax  of  a  uniform  thickness,  a  form  frequently  required  for 
various  purposes  in  the  dental  laboratory. 

The  following  directions  in  the  use  of  wax  will  apply  also 
to  its  combinations  with  paraffin  and  gutta-percha,  and  also  to 
modelling  composition. 

Manner  of  Obtaining  an  Impression  of  the  Mouth  in  Wax 
for  Partial  Upper  Dentures. — Until  within  the  past  few  years, 
wax  has  been  used  almost  exclusively  for  the  purpose  of  ob- 
taining an  impression  of  the  mouth 
in  those  cases  where  any  number 
of  the  natural  teeth  remain  in 
either  or  both  jaws,  and,  for  this 
purpose,  is  ordinarily  more  con- 
venient and  manageable  than  plas- 
ter, and,  if  carefully  manipulated, 
will  secure  in  most  cases  a  sufficiently  accurate  impression  of 
the  parts. 

Before  preparing  the  wax,  a  suitable  cup  or  holder  should 
be  selected  for  the  particular  case  in  hand.  These  appliances 
are  usually  constructed  either  of  plate  or  block-tin,  Britannia 
metal,  or  silver,  and  a  sufficient  number  of  the  various  forms 
required  should  be  provided  to  meet  perfectly  every  require- 
ment in  respect  to  the  size  and  form  of  the  jaws  of  individual 
cases. 

For  upper  partial  or  broken  sets,  the  form  of  cup  repre- 
sented in  Fig.  29  may  be  used.  It  should  be  large  enough  to 
embrace  the  alveolar  ridge,  leaving  a  space  of  nearly  a  fourth 
of  an  inch  between  its  outer  rim  and  the  external  border  of  the 
gum.  If  it  is  designed  to  employ  an  atmospheric  pressure  plate 
covering  nearly  or  quite  all  of  the  hard  palate,  a  cup  of  the  same 
general  form,  but  with  its  central  portion  extended  posteriorly, 


OBTAINING    IMPRESSIONS    OF   THE    MOUTH.  107 

niav  be  used;  or  a  full  cup,  like  that  represented  in  Fig.  31, 
may  be  employed.  Having  selected  a  cup  of  the  proper  form 
and  size,  the  wax  should  be  warmed  in  a  spirit  flame  until  it 
acquires  about  the  consistence  of  freshly  made  putty.  AVax  is 
sometimes  softened  by  immersing  it  in  hot  water,  but  the  dry  heat 
is  preferable,  as  the  former  seems  to  impair,  to  some  extent,  its 
toughness  and  continuity.  In  taking  the  impression  the  oper- 
ator should  place  himself  behind  and  to  the  right  of  the  patient, 
and  should  be  sufficiently  raised  above  the  latter  to  enable  him 
to  manipulate  with  the  greatest  ease  and  certainty,  and  at  the 
same  time  to  command  as  full  and  unobstructed  a  view  of  the 
interior  of  the  mouth  as  possible.  The  cup  with  the  wax  ar- 
ranged should  then  be  introduced  into  the  mouth  without  un- 
necessary  delay.  To  do  this  properly,  and  without  subjecting 
the  patient  to  annoyance,  will  occasionally  require  some  care 
and  expertness,  on  account  of  the  disproportionate  size  of  the 
cup  and  orifice  of  the  mouth.  An  ample  and  expanded  jaw, 
for  example,  is  frequently  associated  with  a  small  mouth,  and 
if  in  addition  to  this  the  sphincter  muscle  of  the  mouth  happens 
to  be  rigid  and  unyielding,  the  introduction  of  a  cup  of  suffi- 
cient size  may  be  attended  with  some  little  difficulty  and  em- 
barrassment. This  impediment,  however,  may  be  readily 
overcome  in  most  cases  by  presenting  the  cup  obliquely  to  the 
mouth,  one  side  resting  against,  and  pressing  outv/ard,  the  cor- 
ner of  the  mouth,  while — as  the  opposite  corner  is  extended 
with  the  first  and  second  fingers  of  the  left  hand — the  cup  is 
passed  in  with  a  rotary  movement. 

When  the  cup  is  within  the  mouth  it  should  be  carefully 
adjusted  over  the  ridge  before  pressing  it  up,  so  that  no  por- 
tions of  the  rim  may  cut  into  the  soft  tissues  of  tlie  mouth,  an 
accident  liable  to  happen  without  care,  and  which  will  make  it 
necessary,  in  most  cases,  to  withdraw  the  cup  before  the  im- 
pression is  complete.  The  jiroper  position  of  the  cup  in  the 
mouth  sef;ured,  it  should  be  held  firmly  with  the  thumb  rest- 
ing on  the  handle  above,  and  two  or  more  of  the  fingers  on  the 
under  surface,  when  it  is  slowly  but  steadily  and  forcibly  })ressed 
against  the  j)arts  above  until  the  ridge  is  completely  imbedded, 


108  MECHANICAL    DENTISTRY. 

and  the  wax  carried  closely  against  the  roof  of  the  mouth. 
The  cup  should  then  be  held  stationary  with  one  hand,  while 
with  the  fingers  of  the  other  the  wax  around  the  margins  of 
the  cup  should  be  pressed  closely  into  all  the  depressions  oc- 
curring on  the  outside  of  the  ridge  between  the  remaining 
teeth,  or  wherever  irregularities  may  present  themselves  on  the 
external  border  of  the  jaw.  The  finger  should  also  be  passed 
to  the  roof  of  the  mouth  at  the  central  and  posterior  edge  of 
the  cup,  making  pressure  against  the  protruding  wax  upward 
and  forward  into  the  anterior  and  deeper  portions  of  the  palatal 
arch.  When  the  operation  has  been  conducted  thus  far,  and 
before  removing  the  cup,  gentle  upward  pressure  upon  the  lat- 
ter may  again  be  made — not  enough  to  move  the  entire  body 
of  wax,  but  only  sufficient  to  correct  any  partial  displacement 
that  may  have  happened  from  accidental  tilting  or  lateral 
movement  of  the  cup  during  the  concluding  manipulations. 

After  the  wax  has  remained  in  the  mouth  long  enough  to 
become  in  some  degree  hardened,  it  should  be  carefully  de- 
tached by  gentle  traction  upon  the  cup,  and  removed  from  the 
mouth  in  the  same  manner  in  which  it  was  introduced ;  care 
being  taken  not  to  displace  the  wax  or  otherwise  mar  the  im- 
pression. More  or  less  dragging  of  the  wax,  however,  will 
unavoidably  occur  in  proportion  as  the  teeth  are  irregularly 
arranged  in  the  arch,  or  have  contracted  necks.  Imperfections 
occurring  from  these  sources  may  be  remedied  with  tolerable 
accuracy  by  subsequent  carving  of  the  plaster  model,  but  the 
better  plan,  where  these  conditions  prevail  to  any  considerable 
extent,  is  to  substitute  gutta-percha  for  wax,  the  elasticity  of 
this  substance  enabling  it  to  regain  the  form  it  acquires  in  the 
mouth  after  having  been  temporarily  disturbed  or  changed  in 
the  act  of  detaching  it  from  the  teeth. 

Inasmuch  as  it  is  necessary,  in  constructing  partial  sets  of  teeth, 
to  be  provided  with  two  or  more  plaster  models,  and  as  the 
latter  cannot  well  be  obtained  in  perfect  condition  from  a  single 
impression,  it  is  better  that  at  least  two  of  the  latter  should  be 
secured  in  the  first  instance. 


OBTAINING   IMPRESSIONS   OF   THE   MOUTH.  109 

Manner  of  Obtaining  an  Imj)ression  of  the  Loicer  Jaw  in 
Wax  for  Partial  Dentures. — If  the  case  is  one  where  teeth  at 
intervals  are  to  be  supplied,  the  form  of  cup  used  in  taking 
an    impression    for   an   entire 
lower  denture  (Fig.   33)  may 
be  employed  ;  or  if  the  vacuity 
exists  in  the  front  part  of  the 
ridge  only,  then  one  like  that 
represented    in    Fig.    29    will 
answer  the  purpose.     If,  how- 
ever, as  is  more  generally  the 
case,   the    front   teeth    remain, 

and  those  posterior  to  the  cuspids  or  bicuspids  are  to  be 
replaced,  the  form  of  cup  exhibited  in  Fig.  30  should  be  used; 
a  portion  being  cut  out  from  the  front  part  of  it,  forming  a 
vacuity  which  receives  and  permits  an  unobstructive  passage 
of  the  front  teeth.  As  the  latter  are  often  very  long,  it  is 
difficult,  with  the  ordinary  form  of  cup,  to  press  the  wax  down 
fairly  upon  the  ridge  behind  without  bringing  their  cutting 
edges  prematurely  in  contact  with  the  floor  of  the  cup  in 
front.  Instead  of  the  ojjcning  represented  in  the  cup,  how- 
ever, it  will  be  sufficient  in  most  cases  to  have  it  formed  with 
a  depression  in  front  of  adequate  depth  to  receive  the  points  of 
the  anterior  teeth. 

In  taking  an  impression  of  the  lower  jaw,  after  having  pre- 
pared and  arranged  the  wax  by  softening  and  filling  the 
groove  of  the  cup  flush  with  the  margins,  the  oj)erat()r  may 
first  take  a  position  to  the  right  and  back  of  the  patient,  and 
introduce  the  cup  into  the  mouth  in  the  manner  heretofore 
described,  when  he  should  pass  to  the  front  of  the  patient, 
and  having  adjusted  the  cup  properly  over  the  ridge,  the  first 
two  or  three  fingers  of  each  hand  should  be  placed  upon  the 
top  of  each  side  of  the  cup,  and  a  thumb  upon  each  side  and 
underneath  the  jaw,  and  firm  and  steady  pressure  made  until 
the  ridge  is  wholly  imbedded.  The  wax  may  then  be  pressed 
in  around  the  margins  of  the  cup,  and  the  impression  carefully 
removed  froin  the  mouth  in  the  manner  before  indicated. 


110  MECHANICAL   DENTISTEY. 

■  Manner  of  Obtaining  an  Impression  of  the  Mouth  in  Wax 
for  Entire  Tlpj^er  Dentwes. — Tlie  form  of  cup  emplojed  in 
taking  an  impression  of  the  upper  jaw  in  the  absence  of  all  the 
natural  teeth,  is  seen  in  Fig.  31.  '  A  number  of  these,  corre- 
sponding as  nearly  as  possible  in 
form  and  size  to  the  various  modi- 
fications in  the  configuration  and 
dimensions  of  the  maxillary  arch, 
should  be  kept  conveniently  at 
hand.  If  the  teeth  have  been  re- 
cently extracted,  the  wax  should 
be  prepared  somewhat  softer  than  usual  to  prevent  displace- 
ment of  the  gums,  which,  in  their  unabsorbed  condition,  pos- 
sess more  or  less  mobility.  The  cup  should  be  filled  flush 
with  the  edges,  and  built  up  in  the  centre  if  the  depth  of  the 
palatal  vault  requires  it,  and  the  wax  properly  trimmed;  it  is 
then  introduced  into  the  mouth  and  adjusted  to  the  ridge,  as 
already  described,  and  pressed  to  the  jaw  with  sufficient  force 
to  fully  encase  all  the  parts  to  which  the  substitute  is  ulti- 
mately to  be  applied.  The  wax,  as  the  cup  is  pressed  up,  has 
a  tendency  to  roll  out  at  its  edges  and  thus  depart  from  the 
upper  and  outer  portions  of  the  ridge;  hence  care  must  be 
taken  to  press  the  wax  in  around  the  marginal  portions  of  the 
cup,  filling  up  any  depressions  or  fosses  that  may  occur  on  the 
external  border  of  the  jaw.  It  is  particularly  necessary  to 
observe  this  precaution  whenever  the  ridge  overhangs,  as  is 
prominently  the  case  for  the  first  few  months  after  the  extrac- 
tion of  the  teeth. 

If  the  impression  is  an  accurate  one,  some  difficulty  is  occa- 
sionally experienced  in  detaching  it  from  the  mouth  on  account 
of  the  thorough  exclusion  of  air  from  between  it  and  the 
mouth,  the  wax  being  held  firmly  in  place  by  atmospheric 
pressure ;  in  which  event  it  is  only  necessary  to  admit  the  air 
between  the  two,  and  this  may  generally  be  readily  effected  by 
placing  the  finger  against  the  jaw  on  one  side  and  above  the 
wax,  pressing  firmly  toward  the  centre  of  the  arch  and 
upward,  dragging  the  mucous  membrane  somewhat  from  the 


OBTAINING  IMPRESSIONS   OF   THE   MOUTH. 


Ill 


edo-e  of  tlie  cup,  and  at  the  same  time  depressing  the  latter  on 
the  same  side.  A  small  portion  of  air  being  admitted,  it  will 
soon  diffuse  itself  between  the  adhering  surfaces  and  allow  the 
wax  to  be  readily  detached.  To  harden  the  wax,  and  thereby 
prevent  it  from  dragging  at  those  points  where  the  ridge  over- 
hangs, or  to  prevent  any  change  of  form  on  the  application  of 
sufficient  force  to  detach  it  from  the  mouth  when  it  adheres 
Avith  great  tenacity,  a  cup  has  been  constructed  with  a  cham- 
ber underneath  into  which  a  stream  of  cold  water  is  admitted. 
Two  short  pipes,  as  will  be  seen  by  .reference  to  Fig.  32,  com- 
municate with  the  chamber,  and  these  again  connect  with  a 


Fig.  32. 


double  tube  fitting  them  closely,  and  united  at  the  other  end 
with  two  gum-elastic  tubes — one  communicating  with  a  vessel 
of  water  conveniently  placed  and  provided  with  a  stop-cock, 
the  other  leading  to  a  spittoon  or  other  waste  place.  The  two 
portions  of  pipe  may  be  disconnected  when  not  in  use.  After 
taking  an  impression  with  this  cup,  and  before  removing  the 
wax  from  the  mouth,  the  two  portions  of  pipe  are  connected 
and  a  continuous  current  of  cold  water  passed  through  the 
chaml)er  by  turning  the  faucet  connected  with  the  tank  ;  when 
sufficiently  hard,  the  wax  is  removed  from  the  mouth  before 
disjointing  the  pipes,  to  prevent  the  water  from  flowing  upon 
the  patient. 

To  provide  more  ])erfectly  against  failure  of  the  wax  being 
carried  closely  against  the  roof  of  the  mouth  in  cases  where 
the  palatal  vault  is  very  deep,  a  piece  may  be  cut  from  the 
central  part  of  the  cup,  the  wax  being  pressed  at  this  point 
upward  and  forward  into  the  deeper  portions  of  the  palatal 
fowia. 


112  MECHANICAL   DENTISTEY. 

The  author  would  express,  in  this  connection,  his  convic- 
tion that  it  is  impracticable,  in  most  cases,  to  obtain  a  fault- 
less impression  of  the  mouth  in  wax  for  full  upper  dentures. 
There  are  points,  not  readily  accessible  to  the  fingers,  where 
the  wax  departs  from  the  external  and  posterior  borders  of 
the  jaw,  and  is  not,  therefore,  susceptible  of  easy  correction ; 
besides,  when  reached  and  the  remedy  applied,  there  is  no 
certain  assurance  that  in  pressing  the  wax  in  at  one  point  we 
are  not  displacing  it  at  another.  For  this  reason,  we  invaria- 
bly use  plaster  in  these  cases,  and  we  have  sufficient  reason  to 
believe  that  the  results  are  more  uniformly  successful. 

Manner  of  Obtaining  an  Impression  of  the  Lower  Jaw  in 
Wax  for  Entire  Dentures. — The  method  pursued  in  securing 
an  impression  of  the  lower  jaw  in  wax  for  an  entire  denture 

differs  in  no  essential  respect  from 

Fig  33 

that  described  when  taking  an 
impression  for  lower  partial 
pieces,  the  form  of  cup  being 
represented  in  Fig.  33.  When 
the  parts  are  imbedded  in  the 
wax,  the  latter  should  be  pressed 
in  around  the  inner  border  of  the 
holder,  but  more  especially  near  the  posterior  part  of  the  ridge 
on  each  side  where  the  latter  overhang  and  approximate  each 
other,  forming  corresponding  excavations  underneath.  After 
adjusting  the  wax  to  the  ridge  along  the  border  of  the  cup,  the 
latter  should  again  be  pressed  directly  down  upon  the  jaw  be- 
fore removing  it,  to  correct  any  partial  deformity  that  may 
have  occurred  during  the  previous  manipulations. 

Gutta-percha. — This  material  is  rarely  used  except  in  ob- 
taining impressions  for  partial  pieces,  and  is  more  particularly 
indispensable  whenever  a  perfect  representation  of  the  parts  in 
plaster  is  essential  to  the  success  of  any  method  in  which  the 
base  is  moulded  or  cast  upon  the  model,  as  in  the  use  of  rub- 
ber, celluloid,  etc.  It  takes  the  form  and  position  of  the  teeth 
readily,  and  preserves  them  unchanged,  by  virtue  of  its  elas- 
ticity, when  removed  from  the  mouth. 


OBTAIXING   IMPRESSIONS    OF    THE    MOUTH.  113 

The  general  management  of  tliis  substance  in  the  process  of 
obtaining  an  impression  Avith  it,  is  in  most  respects  similar  to 
that  of  wax,  when  used  for  the  same  purpose.  It  should, 
however,  be  prepared  by  softening  it  in  hot  water,  but  as  the 
heat  required  to  render  it  sufficiently  plastic  is  greater  than 
could  be  well  endured  without  inflicting  injury  upon  the  soft 
tissues  of  the  mouth,  and  subjecting  the  patient  to  pain  in  its 
application,  it  is  customary,  after  having  heated  it  sufficiently 
and  packed  the  cup,  to  chill  the  surface  by  plunging  it  into 
cold  water,  and  then  introduce  it  quickly  into  the  mouth. 
When  the  impression  is  secured,  and  the  gutta-percha  has  be- 
come somewhat  rigid  in  the  mouth,  it  should  be  removed  and 
filled  immediately  with  plaster,  as  it  contracts  rapidly  in  cool- 
ing. 

Plaster  of  Paris,  or  gypsum,  or  technically,  calcium  sul- 
phate, has  been  long  employed  in  taking  impressions  of  the 
mouth  for  entire  dentures,  and  more  recently  and  to  a  limited 
extent,  for  partial  or  broken  sets.  For  entire  pieces,  it  has 
almost  wholly  suj^erseded  the  use  of  wax,  and  is  better  adapted 
for  receiving  an  accurate  impression  of  the  mouth,  whenever 
it  is  desired  to  secure  a  copy  of  all  its  parts  in  their  undis- 
turbed relation  to  each  other,  than  any  material  that  has  yet 
been  employed. 

When  used  for  this  purpose,  it  should  be  of  the  best  quality, 
finely  pulverized  and  well  sifted,  and  should  always  be  kept 
in  a  closed  vessel,  as  the  moisture  which  it  attracts  from  the 
atmosphere  impairs  its  property  of  hardening  quickly  when 
prepared  for  use.  If  impregnated  with  moisture,  it  should  be 
first  dried  in  a  shallow  vessel  over  a  moderate  heat  before 
being  used. 

It  is  prepared  for  use  by  mixing  with  it  a  sufficient  quantity 
of  water  to  form  a  batter  of  about  the  consistence  of  very 
thick  molasses,  in  which  condition  it  hardens  by  a  species  of 
crystallization  in  from  three  to  five  minutes.  The  condensation 
of  the  plaster  mixture  is  hastened  somewhat  by  the  admixture 
of  a  small  (piantity  of  sodium  chloride  or  common  salt.  The 
best  method   of  preparing  plaster,  however,  for  the  purpose 

8 


114  MECHANICAL   DENTISTRY. 

under  consideration,  is  to  combine  water  with  it  in  sufficient 
quantity  to  form,  in  the  first  place,  a  very  thin  batter,  and 
then  to  stir  or  beat  it  constantly  with  a  small  spatula  until  it 
becomes  sufficiently  thickened  to  admit  of  its  adhering  in  a 
body  to  the  vessel  in  which  it  is  mixed  when  the  latter  is  in- 
verted, and  when  one  portion  will  retain  nearly  its  form  when 
heaped  upon  another.  By  this  process  of  protracted  beating, 
calling  sometimes  "tempering,"  it  is  made  tough  and  pasty, 
without  having  its  plasticity  impaired,  and  when  introduced 
into  the  mouth  in  this  condition,  it  adapts  itself  readily  to  the 
parts,  hardens  quickly,  and  is  not  liable,  with  ordinary  care,  to 
incommode  the  patient  by  running  back  into  the  fauces.  So 
quickly,  indeed,  does  it  condense,  that  unless  expeditiously  in- 
troduced into  the  mouth,  it  will  begin  to  "set"  before  the 
parts  are  fairly  imbedded.  When  preparing  it  for  use,  there- 
fore, the  plaster  should  be  mixed  at  the  chair  with  the  cup 
conveniently  at  hand,  while  the  patient  should  be  in  proper 
position  and  in  immediate  readiness  for  the  operation. 

In  view  of  the  liability  of  the  plaster  to  run  back  into  the 
fauces  when  the  cup  is  pressed  to  its  place  in  the  mouth,  pro- 
ducing nausea  and  involuntary  retching,  and  which  is  very 
liable  to  occur  whenever  the  mixture  is  too  thin  or  is  im- 
properly manipulated,  it  is  recommended  to  instruct  the  patient 
to  avoid  swallowing  while  the  plaster  is  in  the  mouth.  Patients 
are  also  advised  to  breathe  through  the  nostrils,  but  we  see  no 
good  reason  for  this  injunction.  It  should  be  remembered 
that,  in  the  act  of  breathing  through  the  nose,  the  velum  palati  or 
soft  palate  is  depressed  to  cut  off  the  passage  of  air  through  the 
mouth,  and  that  it  is  thus  brought  more  immediately  in  contact 
with  any  portions  of  plaster  that  may  be  protruding  from  the 
heel  of  the  cup.  The  stimulus  of  contact  will  tend  to  produce 
involuntary  contractions  of  the  muscles  of  the  soft  palate  and 
fauces,  and  thus  portions  of  soft,  or  fragments  of  hard,  plaster 
will  be  worked  or  drawn  back  into  the  fauces,  producing  the 
very  evils  it  is  designed  to  avoid.  If,  therefore,  patients  are 
instructed  at  all  in  this  respect,  they  should  be  advised  to 
breathe  naturally  through  the  mouth,  this  channel  affording 


OBTAINING   IMPRESSIONS   OF   THE  MOUTH.  115 

less  obstruction  to  respiration  than  that  through  the  nostrils  in 
the  act  of  taking  an  impression. 

Manner  of  Obtaining  an  Impression  of  the  Movih  in  Plaster 
for  Partial  Upper  Dentures. — There  are  conditions  of  the 
mouth,  incident  to  the  presence  of  natural  teeth  within  it, 
which  would  seem  to  preclude  the  use  of  plaster  in  taking  an 
impression  of  the  parts.  Thus,  if  any  number  of  the  teeth 
remaining  are  small  at  the  necks  with  enlarging  crowns,  or  if 
they  are  irregularly  arranged  in  the  circle,  having'  either  an 
anterior,  posterior,  or  lateral  obliquity,  it  would  not  only  be 
difficult  to  detach  hardened  plaster  from  teeth  so  circum- 
stanced, but  the  force  necessary  to  remove  it  would  inevitably 
break  away  portions  of  plaster  from  around  the  teeth.  Another 
apparent  objection  to  the  use  of  plaster  in  these  cases  consists 
in  the  difficulty  with  which  the  impression  is  separated  from 
the  plaster  model,  it  being  necessary  to  cut  away  the  former 
by  piecemeal,  as  it  would  be  impossible  to  separate  the  two  in 
the  ordinary  Avay. 

The  difficulties  incident  to  the  detachment  of  the  plaster 
from  the  teeth  in  the  mouth  may  be  obviated  in  either  of  the 
following  Avays:  1.  Take  an  impression  first  in  wax,  and  with 
a  metallic  die  and  counter,  obtained  from  a  model  of  the  parts, 
swage  a  plate  of  tin,  brass,  zinc,  or  silver,  of  the  size  and  form 
of  the  intended  base ;  coat  the  palatal  surface  of  this  temporary 
holder  with  a  thin  coating  of  plaster  mixture,  and  apply  it  to 
the  mouth  in  the  manner  usually  employed  in  obtaining  an 
impression. 

2.  Take  an  impression  of  the  parts  in  wax  and  cut  away 
from  tlie  latter  all  those  portions  indented  by  the  teeth,  leaving 
only  so  much  of  the  wax  surface  as  corresponds  with  the  palate 
and  interspaces  in  the  ridge ;  use  this  as  a  holder,  and  secure 
the  impression  by  coating  its  surface,  as  before,  with  a  thin 
layer  of  |)la'^ter  batter.  By  either  of  the  above  methods  an 
impression  of  those  parts,  only,  on  which  the  substitute  is 
designed  to  rest,  can  be  taken ;  the  form  and  position  of  the 
teeth  must  be  scr;ured  in  a  separate  impression  either  with  wax 
or  gutta-percha. 


116 


MECHANICAL   DENTISTRY. 


Notwithstanding  the  obvious  objections  already  stated,  many- 
operators  prefer,  in  taking  impressions  for  partial  cases,  to 
imbed  all  the  parts  in  plaster  in  the  same  manner  as  when 
wax  is  used,  being  careful  to  remove  the  plaster  from  the 
mouth  before  it  has  acquired  the  usual  hardness.  If  the  re- 
maining teeth  have  contracted  necks,  or  are  placed  irregularly 
in  the  arch,  they  may  be  partially  encased  in  wax  before  apply- 
ing the  plaster;  this  will  facilitate  the  withdrawal  of  the  im- 
pression and  preserve  the  form  of  the  teeth  ;  the  wax,  receiving 
the  impress  of  the  teeth,  coming  away  with  the  plaster.  The 
form  of  the  cup  used  in  these  cases  is  the  same  as  that  repre- 
sented in  Fig.  31,  the  edge  of  which  may  be  turned  in  a  little 
at  points  to  prevent  the  plaster  from  being  dragged  from  the 
cup.  The  cup  being  filled  with  the  plaster  mixture  is  intro- 
duced into  the  mouth  and  carefully  pressed  up  until  all  the 

Fig.  34. 


parts  are  fully  imbedded.  When  partial  hardening  of  the 
plaster  has  occurred,  sufficient  tractive  force  should  be  judici- 
ously appKed  to  the  cup  to  separate  the  plaster  from  the  teeth 
and  soft  parts,  when  it  should  be  carefully  removed  from  the 
mouth.  If  any  portion  of  the  plaster,  essential  to  the  form  of 
the  impression,  should  break  away,  the  fragment  or  fragments 
may  be  secured  and  afterwards  applied  to  the  fractured  surfaces. 
Considerable  force  is  sometimes  necessary  to  separate  the 
plaster  from  the  teeth,  and  in  the  effort  to  remove  the  former, 
it  is  liable  to  part  from  the  cup  and  remain  fixed  in  the  mouth ; 
in  which  case  it  will  be  necessary  to  cut  it  away  by  piecemeal. 


OBTAINING    IMPRESSIONS   OF   THE    MOUTH.  1  1 7 

This  casualty  may  be  eifectually  prevented  by  employing  the 
form  of  cup  shown  in  Fig.  34,  contrived  by  Dr.  Samuel  War- 
die,  of  Cincinnati,  and  used  by  him  with  entire  success.  It 
will  be  seen  to  consist  of  an  ordinary  holder,  the  cup  portion 
perforated  in  the  centre,  through  which  a  small  rod  passes  with 
a  screw  cut  on  one  end,  and  the  other  surmounted  with  a  con- 
cave flange,  around  and  underneath  which  the  plaster  collects. 
The  rod  is  formed  with  a  shoulder  resting  on  the  palatal  face 
of  the  cup,  and  is  fixed  in  position  by  screwing  the  tap  against 
the  lower  surface  of  the  holder.  A  number  of  these  centre- 
pieces, with  shafts  of  various  lengths,  should  be  provided,  in 
order  that  any  desired  elevation  may  be  given  to  the  cap  or 
flange ;  for  the  latter  is  designed  not  only  to  confine  the  plaster, 
but  also  to  carry  it  up  into  the  roof  of  the  mouth  where  the 
latter  is  very  deep. 

An  admirable  expedient  for  securing  an  impression  with 
plaster  for  partial  cases  is  thus  described  by  Professor  Charles 
J.  Essig: 

"  An  impression  cup  should  first  be  selected  of  the  proper 
size  and  shape, — those  with  the  flat  floor  are  best  for  partial 
cases ;  the  plaster  should  be  mixed  thin,  almost  as  thin  as  water, 
adding  chloride  of  soda  to  facilitate  setting.  Plaster  mixed  in 
this  manner  does  not  become  as  hard  and  unyielding  as  that 
mixed  merely  to  saturation.  Now  oil  the  cup  so  that  it  will 
readily  separate  from  the  impression  when  hard,  fill  the  cup 
as  soon  as  the  plaster  thickens  sufiiciently,  then,  with  a  small 
spatula,  place  a  layer  of  the  soft  plaster  in  upon  the  palatine 
surface,  otherwise  by  inclosing  the  air  in  the  deep  portion  of 
the  arch  the  accuracy  of  the  impression  may  be  impaired.  After 
this  precaution,  the  cup  is  placed  in  the  mouth,  and  gently 
pressed  up  until  its  floor  comes  in  contact  with  the  teeth.  When 
the  plaster  is  sufiiciently  hardened,  remove  the  cup,  which,  from 
its  having  been  oiled,  is  done  without  difficulty ;  with  the  thumb 
and  index  finger  break  off"  the  outside  walls;  the  portion  cover- 
ing the  j)alatine  surface  is  then  removed  by  the  use  of  a  blunt 
steel  spatula,  curved  at  the  end  in  the  form  of  a  hook.  The 
pieces  are  then  placed  back  into  the  cup,  where  they  will  be 
fijund  to  articulate  with  perfect  accuracy. 


318  MECHANICAL,   DENTISTRY. 

"Should  the  first  attempt  be  rendered  futile,  by  the  tendency 
to  nausea,  or  troublesome  gagging  on  the  part  of  the  patient, 
camphor- water,  as  recommended  by  Dr.  Louis  Jack,  may  be 
used  as  a  gargle,  which  will  in  nearly  every  case,  prove  an  effec- 
tual remedy." 

Manner  of  Obtaining  an  Impression  of  the  Mouth  in  Plaster 
for  Entire  Upper  Dentures. — The  form  of  cup  used  in  securing 
an  impression  of  the  upper  jaw  for  entire  sets  of  teeth,  differs 
in  no  essential  respect  from  that  recommended  when  wax  is 
used  for  similar  purposes.  If  the  external  border  of  the  alve- 
olar ridge  is  very  deep,  or  there  is  considerable  space  interven- 
ing between  the  heel  of  the  cup  and  the  floor  of  the  palate,  a 
rim  of  wax  may  be  placed  along  the  outer  margin  of  the  cup, 
and  extended  across  its  posterior  border,  in  order  more  effectu- 
ally to  confine  the  plaster  within  the  cup  and  prevent  its  escape 
into  the  back  part  of  the  mouth  before  it  has  fairly  reached  the 
palatal  vault.  If  the  latter  is  very  deep,  with  a  marked  excava- 
tion in  its  central  and  anterior  portion,  or  if  it  presents  some- 
what the  form  of  a  deep  fissure,  the  plaster  may  fail  to  be  car- 
ried perfectly  against  the  floor  of  the  palate,  or  the  air  becoming 
confined  within  the  central  portion  of  the  arch,  when  the 
plaster  is  pressed  up,  may  displace  the  latter  and  form  corre- 
sponding chambers  in  the  impression.  If  these  imperfections 
are  but  slight,  they  may  be  subsequently  remedied  either  by 
filling  up  the  cavity  or  cavities  in  the  impression,  or  by  trim- 
ming away  at  these  points  from  the  model.  The  better  plan, 
however,  where  these  conditions  of  the  vault  prevail,  is  to  take 
up  a-  small  portion  of  plaster  on  the  end  of  a  spatula  and  apply 
it  to  the  deeper  portions  of  the  arch  just  before  introducing 
the  cup. 

The  patient  being  seated  as  nearly  upright  in  the  chair  as 
possible,  with  the  head  inclined  slightly  forward,  the  cup  is 
filled  with  the  plaster  mixture  and  introduced  quickly  into  the 
mouth,  when  it  is  pressed  up  slowly  and  gently  until  the  parts 
are  completely  encased  and  portions  of  plaster  are  seen  to  pro- 
trude from  all  parts  of  the  margins  of  the  cup,  otherwise  the 
impression  is  liable  to  be  imperfect  either  on  its  outer  borders 


OBTAIXIXG    IMPRESSIONS   OF   THE    MOUTH.  119 

or  on  its  palatal  face.  Immediately  after  introducing  and  press- 
ing up  the  cup,  the  lip  in  front  should  be  extended  and  drawn 
down  over  the  cup,  when  gentle  pressure,  as  the  plaster  is  hard- 
ening, may  be  made  upon  the  outside  of  the  lip  in  front  and  at 
either  side  of  the  mesial  line  to  force  the  plaster  more  perfectly 
into  the  fosses  which  exist  at  these  points. 

It  is  essential  to  perfect  success  in  this  operation,  that  the 
cup,  after  the  parts  are  once  imbedded,  should  be  held  perfectly 
stationary  until  the  plaster  becomes  fixed,  as  the  slightest  move- 
ment, when  the  plaster  is  in  the  act  of  consolidating,  will  de- 
range the  impression  and  render  it  faulty.  Again,  if  after  the 
parts  are  imbedded,  the  operator  discovers  that  they  are  not 
sufficiently  encased,  and  the  plaster  has  partially  set,  no  further 
effort  should  be  made  to  press  the  plaster  up  upon  the  parts, 
but  the  cup  should  be  withdrawn  and  the  operation  repeated 
with  fresh  plaster. 

If  the  operation  has  been  successfully  conducted,  the  plaster 
will  adhere  to  the  mouth,  in  most  instances,  with  great  tenacity, 
and  it  will  be  necessary  to  observe  some  caution  in  removing 
it,  for,  if  forcibly  detached,  injury  may  be  inflicted  upon  the 
soft  parts  by  tearing  away  portions  of  mucous  membrane;  or 
the  impression  may  be  fractured  or  otherwise  impaired.  In 
addition  to  the  means  already  adverted  to  in  connection  with 
the  method  of  separating  wax  impressions  from  the  mouth,  re- 
sort is  sometimes  had  to  the  following  expedient:  The  central 
portion  of  the  cup  being  pierced  with  two  or  three  small  holes, 
a  blunt-pointed  ])robe  is  passed  at  these  points  through  the 
plaster,  before  tlie  latter  has  hardened  perfectly,  to  the  roof  of 
the  mouth.  Into  these  passages  the  external  air  passes  and 
diffuses  itself  between  the  surface  of  the  plaster  and  the  palate, 
when  the  impression  may  be  readily  detached.  The  author 
has  succeeded  best  in  detaching  impressions  in  such  cases,  by 
upward  and  interrupted  traction  u])()n  the  handle  of  the  cup, 
which,  by  depressing  the  heel  of  the  same,  more  readily  permits 
the  introduction  of  air  than  by  either  of  the  methods  commonly 
cnij)loyed. 

Manner  of  Obtaining  an  Impression  of  the  Mouth  in  Plaster 


120  MECHANICAL    DENTISTRY. 

for  Entire  Lower  Dentures. — Until  recently,  wax  has  been  al- 
most invariably  used  in  taking  impressions  of  the  lower  jaw. 
Plaster,  however,  may  be  used  for  the  same  purpose,  and,  by 
some,  is  esteemed  superior  to  the  former.  The  ordinary  wax- 
holder  as  shown  in  Fig,  32  may  be  used,  and  which,  being 
filled  with  the  plaster  batter  thoroughly  beaten  until  quite 
tough  and  pasty,  is  inverted  and  quickly  introduced  into  the 
mouth  and  pressed  down  upon  the  ridge  until  the  latter  is 
completely  imbedded;  when  sufficiently  hard  it  should  be  re- 
moved in  the  ordinary  way. 

In  securing  an  impression  of  the  lower  ridge  in  plaster, 
better  results  can,  in  many  cases,  be  obtained  by  first  taking 
the  impression  in  wax,  enlarging  the  impression  thus  secured 
with  suitable  instruments,  and  using  this  as  a  tray  for  plaster. 

A  form  of  tray,  contrived  expressly  for  the  use  of  plaster 
by  Dr.  B.  W.  Franklin,  is  exhibited  in  Fig.  35.  It  consists 
of  two  chambers,  or  a  double  groove,  communicating  with  each 


other  by  a  fissure  running  from  heel  to  heel  of  the  cup.  The 
groove  corresponding  with  the  curvature  of  the  lower  jaw  is 
filled  with  plaster  properly  prepared,  inverted,  passed  into  the 
mouth,  and  pressed  down  upon  the  parts.  As  the  cup  is  pressed 
down,  portions  of  plaster  will  be  forced  through  the  fissure  into 
the  upper  chamber, — this  should  be  pressed  down  at  all  points 
along  the  groove  with  the  finger,  securing  more  perfectly,  in 
this  manner,  the  intrusion  of  the  plaster  into  any  irregularities 
or  depressions  that  may  occur  in  the  ridge.  Or,  the  empty 
cup  may  be  placed  in  its  proper  position  over  the  jaw  and  the 
plaster  introduced  into  the  upper  groove  and  pressed  down 
with  the  fingers  through  the  fissure  on  to  the  ridge,  filling  the 
depending  chamber. 


PLASTER    MODELS.  121 


CHAPTER   III. 

Plaster  Models. 

After  an  impression  of  the  mouth  has  been  secured  in 
either  of  the  ways  mentioned  in  the  preceding  chapter,  the  next 
step  in  the  process  of  constructing  an  artificial  denture  is  to 
procure  from  the  impression  a  representation  of  the  parts  in 
plaster.  The  copy  thus  secured  is  called  a  model,  and,  if  cor- 
rectly obtained,  is  a  true  counterpart  or  fac-simile  of  all  parts 
of  the  mouth  represented  in  the  impression. 

Planner  of  Obtaining  a  Plaster  Model  from  an  Impression  in 
Wax  for  Partial  Dentures. — The  impression  in  wax  should  be 
first  trimmed  by  cutting  away  superfluous  portions  that  over- 
hang the  borders  of  the  cup,  care  being  taken  not  to  mar  any 
essential  })art  of  the  impression.  The  surface  of  the  wax  im- 
printe<l  should  then  be  uniformly  smeared  with  a  thin  coating 
of  oil  applied  with  a  carael's-hair  brush.  The  oil  should  not 
be  of  too  thick  a  consistence,  nor  applied  in  too  large  quan- 
tities, as  it  will  collect  in  the  more  depending  portions  of  the 
impression,  and  failing  to  be  displaced  by  the  plaster,  will 
leave  the  model  imperfect  at  these  points,  especially  at  the 
coronal  extremities  of  the  plaster  teeth.  The  cup  is  now  sur- 
rounded by  some  substance  that  will  confine  the  plaster  and 
give  ])roper  form  to  the  body  of  the  model.  For  this  purpose 
any  material  that  is  easily  shaped  may  be  used,  as  a  thin  sheet 
of  lead  or  wax,  paper,  stri|:>s  of  oil  or  wax  cloth,  etc. 

Before  pouring  the  plaster,  if  it  is  desired  to  strengthen  any 
of  the  plaster  teeth — as  those  adjoining  the  vacuities  in  the 
jaw,  or  such  as  are  to  be  used  in  adjusting  clasps,  and  thus 
secure  them  against  accident  in  handling — adequate  support 
may  Vxi  im))arte<l  to  them  by  placing  short  pieces  of  stiff  wire 
verti(;ally  in  the  depressions  made  in  the  wax  by  the  teeth,  and 


122  MECHANICAL    DENTISTRY. 

which  may  be  supported  in  an  upright  position  by  imbedding 
one  end  in  the  wax  in  the  centre  of  the  bottom  of  each  cavity. 

When  the  cup  is  properly  inclosed  a  batter  of  plaster,  of  some- 
what thinner  consistence  than  that  used  for  impressions,  is  poured 
in  upon  the  surface  of  the  wax  in  sufficient  quantity  to  give  to 
the  body  of  the  model  a  depth  of  from  one  to  three  inches,  ac- 
cording to  the  particular  requirements  of  the  case.  The  plaster 
should  not  be  poured  directly  or  hastily  into  the  cavities  formed 
by  the  teeth,  but  upon  points  contiguous  to  them,  and  from 
which  it  should  be  allowed  to  run  slowly  into  the  depressions, 
expelling  the  contained  oil  or  air,  and  filling  them  perfectly. 
When  the  plaster  has  become  sufficiently  hard,  any  portions 
overlapping  the  borders  of  the  wax,  and  not  essential  to  the 
form  of  the  model,  should  be  cut  away,  and  the  two  separated 
either  by  immersion  in  warm  water,  or  by  placing  the  model 
over  the  flame  of  a  spirit-lamp  or  upon  a  heated  surface,  until 
the  warmth  imparted  to  the  model  renders  the  wax  sufficiently 
soft  to  allow  the  former  to  be  removed  without  fracturing  the 
plaster  teeth.  The  latter  methods  should  be  adopted  whenever 
it  is  desired  to  obtain  duplicate  copies  from  the  same  impres- 
sion, as  by  the  use  of  hot  water  the  impression  is  destroyed, 
the  latter,  however,  being  generally  used  when  gutta-percha  is 
employed.  When  separated  from  the  impression,  the  model 
should  be  properly  trimmed  and  shaped  with  a  knife-blade. 

The  general  form  of  the  body  of  a  model  is  shown  in  Fig. 
36.  The  walls,  as  it  will  be  seen,  are  made  as  nearly  vertical 
or  parallel  as  will  admit  of  the  model  being  readily  detached 
from  the  sand  in  the  process  of  moulding;  for  if  made  too  flar- 
ing or  divergent,  the  metallic  die  obtained  from  it  will  be  more 
liable  to  crack  or  spread  apart  under  the  repeated  strokes  of  a 
heavy  hammer,  or  to  rock  under  one-sided  blows. 

During  the  process  of  stamping  or  forcing  a  metallic  base 
into  adaptation  to  the  die — which  is  a  metallic  counterpart  of 
the  model — the  plate,  when  cut  to  the  exact  pattern  of  the  parts 
to  be  covered  by  it,  is  frequently  forced  or  dragged  back  toward 
the  heel  of  the  die,  and  is  thus  drawn  from  the  teeth  at  the 
sides  and  in  front.     This  displacement  of  the  plate  may  be 


PLA8TER    MODEI.8. 


123 


prevented  by  cutting  away  all   of  the  plaster  teeth  from  the 
model,  leaving,  however,  encjugh  of  them  remaining  where 
they  unite  with  the  body  of  the  model  to  form  a  shoulder  to 
each  tooth,  as  in  Fig.  30.     In  this 
«ise  the  plate  should  besufficiently  i-'k;.  ■%. 

ample  in  its  dimensions  to  parti- 
ally overlap  the  border,  when,  as 
it  is  forced  into  adaj)tation,  distinct 
indentations  will  be  made  in  it, 
corresponding  exactly  with  the  pa- 
latal curvaturfiS  of  the  teeth  ;  the 
portions  of  the  plate  covering  the 
cut  ends  of  the  teeth  are  then  cut 
away  with  plate  forceps  or  other 

instruments,  li',  however,  the  plate  is  of  the  exact  size  re- 
quired before  stamping,  one  f)r  two  plaster  teeth  upon  f;ac-h  side 
of  the  model  maybe  allowed  to  remain,  against  the  anterior 
face  of  which  the  plate  is  made  to  rest  holding  it  stationary. 

Manner  of  Ohtainiru/  a  Pluder  Model  frcmi  an  Imjjression 
in  Wax  for  Entire  Denturea. — Tlie  same  general  method  is 
pursued  in  obtaining  a  plaster   model  from  an  imjiression  in 


Fk;.;57. 


wax  of  cither  the  up[)er  or  lower  jaw  for  entire  denturcis,  as 
that  employed  in  [>artial  f^s^-s.  The  general  form  of  thfise 
p'lecjiH  is  represented  in  Figs.  37  and  38. 

li'  it  is  desired  to  swage  a  rim  to  the  plate,  forming  a  groove 


124  MECHANICAL.   DENTISTRY. 

or  socket  into  which  the  plate  extremities  of  the  teeth  are 
received,  the  model  should  be  formed  in  the  manner  repre- 
sented in  the  annexed  cuts ;  in  which  it  will  be  seen  that  an 
abrupt  shoulder  is  formed  on  the  external  border  of  the  model 
of  the  upper  jaw  (Fig.  37),  but  which  on  the  lower  (Fig. 
38),  is  extended  round  the  inner  border  also,  as  it  is  desirable, 
in  the  latter  case,  to  give  a  rounded  edge  to  the  lingual  border 
of  the  plate,  and  which  is  accomplished  in  part  by  swaging  in 
the  fii"«t  instance  and  afterwards  by  turning  the  edge  down 
upon  the  plate  with  pliers  or  by  other  means.  The  model  is 
prepared  by  adjusting  a  strip  of  softened  wax  around  the  bor- 
der and  cutting  away  from  its  upper  surface  in  such  a  way  as 
to  form  a  groove,  the  bottom  of  which  shall  be  on  a  line  with 
the  extreme  edge  of  the  base  or  plate,  and  which  should  be  in- 
dicated upon  the  model  with  a  pencil-mark  before  applying 
the  roll  of  wax.  Plaster  may  be  substituted  for  wax,  and 
should  always  be  used  whenever  heat  is  applied  to  the  model 
in  the  process  of  obtaining  a  metallic  swage,  as  by  the  "  dip- 
ping" method. 

If  the  model  is  to  be  used  in  moulding,  the  groove  should 
be  sufficiently  open  to  permit  the  ready  withdrawal  of  the 
sand,  otherwise  the  die  at  this  part  will  be  imperfect ;  if,  how- 
ever, the  face  of  the  model  is  to  be  immersed  in  molten  metal, 
securing  first  the  counter-die,  any  form  may  be  given  to  the 
groove  that  will  best  facilitate  the  operation  of  overturning 
the  margins  of  the  plate. 

Rimmed  plates  are  only  required  when  single  gum  teeth  or 
sectional  or  entire  blocks  are  employed,  or  when  plate  teeth 
are  mounted  on  a  platinum  base  with  continuous  gum. 

Whenever  an  air-chamber  is  to  be  stamped  in  the  base,  the 
model  should  be  prepared  for  the  purpose  before  casting  the 
metallic  swages.  The  general  form  and  position  of  the  central 
cavity  or  chamber  in  the  arch  is  represented  in  Fig.  37.  The 
model  may  be  prepared  in  either  the  following  ways :  1.  The 
form  of  the  chamber  may  be  cut  from  the  wax  or  plaster 
impression ;  in  which  case  the  plaster  will  be  raised  at  a  cor- 
responding point  or  points  upon  the  model,  and  will  have  ex- 
actly the  same  form  and  depth  as  the  cavity  in  the  impression. 


PLASTER   MODELvS.  125 

2.  Cover  the  palatal  face  of  the  model  with  a  sheet  of  wax 
equal  in  thickness  to  the  required  depth  of  the  chamber,  and 
cut  out  from  this,  at  the  desired  point,  the  form  of  the  cavity ; 
fill  the  latter  with  plaster,  and  when  hard  remove  the  wax 
and  trim  the  raised  portion  to  the  proper  form.  3.  Cut  a  pat- 
tern chamber,  of  the  required  form  and  thickness,  from  sheet 
wax  or  lead ;  place  it  in  proper  position  in  the  arch  and  press 
down  with  the  fingers  or  burnisher  until  it  conforms  to  the 
contour  of  the  palate;  it  is  then  fixed  in  place  either  by  con- 
fining it  with  a  small  piece  of  wire  or  tack  driven  through  it 
into  the  plaster,  or  by  interposing  softened  wax  or  other  adhe- 
sive material  between  the  chamber  and  model.  A  small  brush 
loaded  with  a  varnish  mixture  passed  round  the  edge  of  the 
chamber  will  insure  sufficient  adhesion  of  the  latter. 

The  same  general  method  as  that  when  central  chambers 
are  formed  is  pursued  in  the  preparation  of  the  model  when  it 
is  desired  to  construct  lateral  cavities  in  the  plate.  The  form 
and  position  of  these  on  the  model  will  be  indicated  by  inspec- 
tion of  the  form  of  "  lateral  cavity  "  plates  as  exhibited  in  the 
chapter  on  "  Entire  Dentures." 

There  are  other  modifications  in  the  form  of  cavity  plates, 
some  of  which  are  obsolete;  that  known  as  "Cleveland's 
chamber"  is  still  in  limited  use,  and  will  be  described  in  a 
subsequent  chapter,  but  does  not  require  a  model  differing  in 
form  from  the  one  described  in  connection  with  full  dentures 
wdth  central  chambers. 

Manner  of  Obtaining  a  Plaster  3Iodel  from  an  Impression 
in  Plaster  for  Partial  Dentures. — The  surface  of  the  impres- 
sion in  plaster  should  first  be  rendered  hard  by  applying  to  it, 
with  a  camel's-hair  brush,  a  uniform  coating  of  varnish  to 
prevent  adhesion  of  the  model.  Two  kinds  of  varnish  are  in 
common  use — a  transparent  and  colored.  Tlie  former  is  pre- 
ferred for  the  reason  that  it  penetrates  the  plaster  more  thor- 
oughly, giving  to  it  a  greater  depth  of  surface  hardness,  while 
the  latter,  if  not  sufficiently  fluid,  forms  a  somewhat  sui)erticial 
incrustation,  which  is  liable  to  peel  off  in   handling,  leaving 


126  MECHANICAL   DENTISTRY. 

portions  of  the  model  unprotected.     Either,  however,  if  prop- 
erly prepared  and  applied,  may  be  employed. 

Formula  No.  1,  Formula  No.  2. 

Transparent  Varnish.  Colored  Varnish. 

Gum  sandarach,        .     5  oz.  Gum  shellac,    .         .     5  oz. 

Alcohol,    .         .         .1  quart.  Alcohol,  .         .         .1  quart. 

The  sandarach  and  shellac  should  first  be  freed  from  all 
impurities  by  careful  jjicking  and  washing ;  they  are  then 
added  to  the  alcohol  and  digested  over  a  moderate  heat  until 
thoroughly  dissolved.  Other  substances,  as  gum  elemi,  Ve- 
nice turpentine,  etc.,  have  been  recommended  as  additional 
ingredients,  but  they  are  not  indispensable,  and  may  be 'omitted 
without  sensibly  impairing  the  properties  of  the  varnish. 

After  glazing  the  surface  of  the  plaster  impression  with  var- 
nish a  thin  and  uniform  coat  of  oil  should  be  applied ;  it  is 
then  enveloped,  and  the  model  procured  in  the  same  manner 
as  when  wax  is  used. 

The  following  method  of  preparing  the  plaster  impression 
before  it  is  filled  in  for  the  model  is  recommended  by  Dr.  C. 
W.  Spalding :  "  After  the  impression  has  become  hard,  coat 
the  surface  with  a  lather  of  soap  and  water ;  wash  this  off  and 
immerse  the  model  in  water.  This  expels  air  and  avoids  lia- 
bility to  porosity  of  the  surface  of  the  model.  Again  coat  the 
surface  with  a  strong  lather  of  soap  and  water,  and  wash  off  as 
before,  when  the  impression  is  ready  to  receive  the  plaster  for 
the  model.  I  prefer  this  method  to  varnishing  for  the  reason 
that  the  varnish  used  is  not  always  of  uniform  consistenc.e." 

In  separating  the  model  from  a  plaster  impression,  for  par- 
tial cases,  it  will  be  necessary  to  cut  the  latter  away  in  pieces, 
as  any  attempt  to  separate  the  two  in  the  ordinary  manner 
would  inevitably  break  away  the  plaster  teeth  from  the  model. 
The  impression  should  be  chipped  away  with  great  care,  to 
avoid  defacing  the  model.  To  provide  more  perfectly  against 
this  accident,  it  is  better  to  coat  the  impression  with  colored 


PLASTER    MODELS.  127 

varnish,*  as  this  will  indicate  with  greater  certainty  the  line  of 
contact  or  union  between  the  two  pieces.  When  separated, 
the  model  should  be  trimmed  and  formed  in  the  manner  here- 
tofore described. 

Manner  of  Obtaining  a  Plaster  3Iodel  from  an  Impression 
in  Plaster  for  Entire  Dentures. — -The  preparation  of  a  plaster 
impression  of  either  the  upper  or  lower  jaw  for  full  dentures, 
and  the  method  of  procuring  a  model  therefrom,  differ  in  no 
essential  respect,  except  in  the  mode  of  separation,  from  the 
manipulations  required  when  the  impression  has  been  taken  in 
plaster  for  partial  pieces.  A  model  can,  ordinarily,  be  readily 
detached  from  an  impression  of  the  lower  jaw,  but  is  not  always 
so  easily  effected  in  the  case  of  the  upper.  To  accomplish  this 
in  the  latter  case,  the  model  may  be  taken  in  the  hand  and  the 
back  of  the  handle  of  the  cup  tapped  lightly  with  an  instru- 
ment; or,  a  small,  wedge-shaped  instrument  may  be  carefully 
forced  between  the  model  and  impression  at  the  posterior  bor- 
der of  the  latter  until  they  part  slightly,  when  they  may  be 
easily  detached ;  before  doing  which,  however,  any  overlap- 
ping portions  of  the  model  which  may  tend  to  bind  the  two 
pieces  together  should  be  trimmed  away.  If  any  portion  of 
the  heel  of  the  model  is  defaced  by  the  introduction  of  the 
wedge,  it  may  be  afterwards  remedied  by  restoring  the  con- 
tour of  the  parts  with  either  wax  or  plaster. 

After  obtaining  a  model  in  either  of  the  ways  mentioned, 
the  entire  body  of  it  should  be  glazed  and  hardened  by  apply- 
ing to  it  a  uniform  coat  of  varnish.  This  protective  covering 
will  prevent  the  surface  from  wearing,  render  it  more  pleasant 
to  the  touch,  facilitate  its  withdrawal  from  the  sand,  and  give 
a  more  perfect  mould.  A  model  may  be  better  prepared  for 
permanent  preservation  by  immersing  it  for  a  short  time  in 
a  solution  of  carbonate  of  soda,  by  which  its  surface  is  con- 
verted into  carbonate  of  lime,  and  thereby  rendered  hard  and 
durable;  care  must  be  taken  not  to  introduce  any  of  the  bicar- 
bonate of  soda  into  the  solution. 


*  The  author  is  indebted  to  Dr.  Spalding  for  a  simple  and  admirable  de- 
vice for  the  Hame  purjjoso,  wliicli  consists  in  coloring  the  water  used  to  mix 
plas'er  for  the  impression  with  aniline  red. 


128  MECHANICAL   DENTISTRY. 


CHAPTER   ly. 

Metallic  Dies  and  Counter-Dies.' 

A  metallic  die  is  a  fae  simile  or  transcript  of  the  mouth 
in  metal,  and  is  also  a  copy  or  likeness  of  the  plaster  model. 

A  metallic  counter-die  is  a  copy  of  the  impression,  and  is 
a  reversed  image  of  the  die  and  plaster  model. 

Manner  of  Obtaining  a  Metallic  Die. — Two  general  methods 
are  employed  in  procuring  a  metallic  counterpart  of  the  model ; 
first,  by  moulding;  secondly,  by  a  process  termed  "dipping." 

Moulding. — For  this  purpose  the  best  material  is  marble- 
dust,  though  other  substances — as  sand,  Spanish  whiting,  etc. 
— have  been  recommended.  Marble-dust  has  the  advantage 
of  being  always  ready  for  use,  as  it  absorbs  sufficient  moisture 
from  the  atmosphere  to  render  it  cohesive,  is  cleanly,  and  gives 
a  smooth  and  uniform  surface  to  the  die.  When  sand  is  used 
it  should  be  fine  and  even-grained,  the  best  for  the  purpose 
being  that  used  by  brassfounders.  It  is  prepared  by  mixing 
with  it  sufficient  water  to  render  its  particles  somewhat  adhe- 
rent, so  that  when  portions  of  it  are  pressed  in  the  hand  and 
then  parted  with  the  fingers  it  will  break  away  in  well-defined 
fragments.  Excess  of  water  should  be  avoided,  as  the  vapor 
formed  by  the  molten  metal,  when  poured  upon  it,  will  dis- 
place portions  of  the  latter,  and  form  cavities  or  blisters  in  the 
face  of  the  die ;  nor  should  the  sand  used  be  too  dry,  as  in 
that  case  it  will  crumble  away  in  detaching  the  model. 

Oil  has  been  proposed  as  a  substitute  for  water,  in  which 
case  it  is  recommended  to  add  one  quart  of  the  former  to  a 
peck  of  sand.  It  is  claimed  that  the  sand  so  prepared  is 
always  in  immediate  readiness  for  use. 

The  moulding  material  properly  prepared,  the  model  is  next 
placed  with  its  face  uppermost,  on  the  moulding-board,  and 


METALLIC    DIES   AND    COUNTER-DIES.  129 

surrounded  with  a  metallic  ring.  A  common  "  wagon-box," 
of  which  two  or  three  sizes  should  be  had,  will  answer  every 
purpose.  If  sand  is  used  it  should  first  be  well  sifted  to 
remove  the  coarser  particles,  and  then  filled  into  the  ring, 
packing  it  closely  with  the  fingers  around  and  over  the  model 
until  even  with  the  upper  edge  of  the  box.  Some  care  must 
be  observed  in  the  management  of  the  moulding  material 
when  packing  it,  for,  if  made  too  compact,  the  vapor  formed  in 
pouring  hot  metal,  failing  to  pass  out  readily,  will  be  confined 
within  the  cavity,  and  form  imperfections  in  the  face  of  the 
die;  or,  if  too  loosely  packed,  the  fluid  metal,  when  poured 
into  the  mould,  will,  to  some  extent,  permeate  the  pores  of  the 
sand  or  other  material,  and  render  the  face  of  the  die  rough 
and  imperfect. 

The  box,  with  the  model  encased,  is  then  lifted  above  the 
board  and  the  model  dislodged  by  tapping  it  gently  under- 
neath Avith  a  small  mallet  or  hammer  until  it  parts  from  the 
mould.  The  uncertain  and  hazardous  method,  sometimes  re- 
sorted to,  of  detacliing  the  model  by  pressing  it  alternately 
backward  and  forward  until  loosened,  and  then  lifting  it  out, 
should  never  be  practiced,  as  more  or  less  deformity  of  the 
mould  is  unavoidably  produced  thereby. 

It  not  unfrequently  happens  that  the  ridge  on  the  plaster 
model  of  the  upper  jaw  overhangs,  forming  corresponding 
depressioas  above,  the  excavations  occurring  more  commonly 
in  front  and  on  each  side  of  the  mesial  line.  Whenever  this 
form  of  the  model  exists,  it  will  be  impracticable  to  obtain  a 
correct  mould  in  the  manner  just  described,  since  the  sand 
becoming  impacted  in  these  excavations  will  be  broken  away 
and  remain  with  the  model  when  the  latter  is  dislodged. 

The  difficulty  mentioned,  however,  may  be  readily  over- 
come in  all  cases  by  employing  the  sectional  moulding  flask 
iiivented  by  Dr.  G.  W.  Hawes,  the  several  parts  of  which  are 
represent<id  in  the  accompanying  cuts. 

Fig.  30  represents  the  lower  ring,  composed  of  three  mov- 
able pieces  with  flange  extensions,  which  project  in  toward  the 
centre,     ^\l^en  used,  this  portion  of  the  flask  is  closed  and  the 


130 


MECHANICAL   DENTISTEY. 


sections  kept  in  place  by  pins  passing  through  the  joints. 
Inside  of  this  ring  the  model  is  placed  face  upward,  the  ridge 
extending  a  little  above  the  upper  plane  of  the  ring.  Sand, 
well  sifted,  is  then  packed  in  around  the  model  on  a  level  with 
the  most  projecting  points  on  the  outside  of  the  ridge,  as  indi- 
cated by  the  dotted  line  in  Fig.  41.  The  surface  of  the  sand 
should  be  trimmed  smoothly,  and  should  be  cut  squarely  and 
at  right  angles  with  the  ridge,  to  prevent  the  sand  from  break- 
ing away  when  the  model  is  withdrawn.  Very  finely  pulver- 
ized charcoal  contained  in  a  loose  muslin  bag  is  now  sifted 


Fig.  39. 


Fig.  40. 


Fig.  41. 


over  the  exposed  surface  of  the  sand,  to  prevent  the  next  por- 
tion contained  in  the  upper  ring  from  adhering.  ^  The  plain 
ring  (Fig.  40)  is  then  placed  over  the  one  containing  the 
model,  and  is  filled  with  sand  well  packed  over  the  face  of  the 
die.  The  upper  ring  is  now  carefully  lifted  from  the  lower 
one  on  a  line  with  the  pins,  thus  separating  the  two  portions 
of  sand,  and  again  exposing  the  uncovered  face  of  the  model. 
One  of  the  pins  should  then  be  drawn  from  the  lower  ring ; 
the  sections  of  the  latter  carefully  unfolded,  and  the  model 
withdrawn ;  when  the  ring  may  be  again  closed  and  confined 
by  replacing  the  pin.     The  upper  ring  is  then  readjusted  in 


METALLIC    DIES    AND    COUXTER-DIES.  131 

its  proper  relation  to  the  lower  one,  and  the  flask  inverted  ; 
when  the  mould,  if  the  process  has  been  accurately  conducted, 
will  be  found  perfect. 

In  the  absence  of  the  "  Hawes"  flask,  the  same  results  may 
be  attained  by  employing  the  following  simple  method,  re- 
commended by  Dr.  Berhard,  and  substantially  described  as  t 
follows :  "  The  plaster  model  being  prepared  in  the  usual  man- 
ner for  moulding,  varnish  the  front  (or  the  whole)  with  a  thin 
solution  of  shellac.  When  dry,  apply  a  mixture  of  plaster  of 
proper  consistence  to  the  front  of  the  model  from  the  bottom 
up  to  the  edge  of  the  alveolar  line,  spreading  it  on  both  sides 
so  as  to  entirely  fill  up  the  depression  around,  making  the 
bottom  half  an  inch  thick,  and  sloping  off  toward  the  alveolar 
ridge.  When  this  has  hardened,  separate  it  from  the  model, 
and  draw  the  top  of  it  over  sandpaper  to  obtain  a  flat  edge,  and 
let  it  dry.  Readjust  this  front  piece  to  the  model ;  procure  a 
mould  in  sand  or  other  material  in  the  usual  way;  place  the 
extra  piece  back  in  its  proper  position  in  the  mould,  and  pro- 
ceed to  cast  for  the  die," 

In  obtaining  a  mould  from  the  model  of  a  lower  jaw,  but 
little  difficulty  will  ordinarily  be  experienced  in  obtaining  it 
perfect  in  the  manner  first  described.  The  depressions  at  the 
posterior  and  inner  border  of  the  ridge  are  the  points  most 
liable  to  drag  or  displace  the  sand,  and  when  the  latter  occurs, 
the  surplus  metal  in  the  die  at  such  points  must  be  cut  away 
with  suitable  instruments ;  or  the  cavities  in  the  model  may  be 
so  filled  out  with  wax  before  moulding  as  to  permit  the  ready 
separation  of  the  model  without  displacing  the  sand,  in  which 
case,  also,  it  will  be  necessary,  afterward,  to  trim  the  redun- 
dant metal  from  the  die. 

A  die  is  more  readily  and  accurately  ol)tained  from  a  model 
for  partial  dentures  by  cutting  away  the  plaster  teeth  as  before 
described.  The  displacement  of  sand  where  the  ridge  over- 
hangs will,  as  a  general  thing,  be  unimportant  in  these  cases, 
as  the  base  but  rarely  more  than  partially  overlaps  the  border. 

When  whiting  or  marble-dust  is  used  in  moulding,  it  is  un- 
necessary to  mix  water  with  them,  as  the  moisture  which  they 


132  MECHANICAL    DENTISTEY. 

absorb  from  the  atmosphere  will  give  to  them  the  proper  con- 
sistence. 

Having  obtained  a  mould  in  either  of  the  ways  mentioned, 
the  metal  designed  for  the  die  shonld  be  melted  and  poured 
carefully  in  upon  the  more  prominent  portions  on  the  face  of 
the  former.  If  the  metal  is  raised  much  above  its  fusing- 
point,  or  the  sand  is  quite  damp,  the  former  should  be  poured 
very  slowly  into  the  mould.  It  is  better,  however,  that  the 
sand  should  be  partially  dried  before  pouring  the  metal,  and 
the  die  cast  on  the  instant  of  the  metal  becoming  sufficiently 
fluid.  An  observance  of  these  precautions  will  protect  the 
sand  from  the  overaction  of  heat,  prevent  ebullition  of  the 
fused  metal  from  the  too  rapid  decomposition  of  the  water  of 
the  sand,  and  will  give  a  smoother  face  to  the  die,  and  secure 
the  metal  or  metals  from  undue  waste  by  oxidation.  The 
opinion  is  entertained  by  some  that  greater  shrinkage  of  the 
die  occurs  when  the  metallic  substance  of  which  it  is  composed 
is  poured  at  a  temperature  much  above  its  fusing-point;  the 
fallacy  of  this  is  made  obvious  by  a  moment's  reflection,  as  a 
simple  example  will  show  that  any  change  affecting  the  face  of 
the  die,  as  a  consequence  of  contraction,  can  only  occur  in  the 
metal  between  its  point  of  solidification  or  liquefaction — for 
they  are  identical — and  its  working  temperature.  Zinc,  for 
example,  melts  at  773°.  Now  if  its  temperature  be  raised  to 
1200°,  it  will  remain  fluid  until  it  reaches  773°,  and  in  passing 
through  the  intermediate  degrees  of  heat,  it  will,  in  obedience 
to  gravity,  adapt  itself  perfectly  to  all  parts  of  the  more  de- 
pending portions  of  the  mould ;  and  this  perfect  continuity  of 
the  two  surfaces  will  remain  unaffected  by  the  contraction  of 
the  metal  until  the  latter  commences  to  "set,"  or  solidify 
(773°),  after  which,  and  not  until  then,  the  zinc  begins  to  part 
from  the  face  of  the  mould  by  contracting  upon  itself  between 
773°  and  the  mean  temperature  of  the  air.  So  far  as  any 
change,  by  contraction,  in  the  face  of  the  die  is  concerned, 
therefore,  it  is  obviously  immaterial  whether  the  zinc  be 
poured  on  the  instant  of  melting  or  at  1200°;  the  result  will 
be  the  same  in  either  case. 


METALLIC    DIES    AND    COUNTER-DIES.  133 

The  author  is  indebted  to  Dr.  B.  W.  Franklin  for  the  fol- 
lowing method  of  securing  metallic  dies  and  counters  by  a  pro- 
cess which  greatly  facilitates  the  operation  and  insures  accurate 
and  satisfactory  results :  "  I  take  all  impressions,  full  and  par- 
tial, in  plaster.  A  small  hole,  less  than  tV  inch,  is  drilled 
through  the  highest  point  of  the  palatal  surface  of  the  impres- 
sion through  cup  and  all ;  into  this  place  two  or  three  broom 
splints,  cutting  them  oft'  even  with  the  surface  of  the  plaster, 
to  allow  any  vapors  to  pass  off.  I  sometimes  smoke  the  sur- 
face of  the  impression.  Around  the  impression  place  sufficient 
putty  to  form  a  ring  the  size  and  height  required  for  the  die. 
Into  this  pour,  at  as  low  heat  as  consistent  with  the  mobility 
required  for  sharp  castings,  the  bismuth  alloy  known  as  Sir 
Isaac  Newton  metal,  or,  which  is  better  in  some  respects,  8 
parts  bismuth  and  4  parts  each  of  tin  and  lead — the  latter 
composition  being  a  little  harder.  If  a  little  judgment  is  ex- 
ercised in  pouring  either  of  the  above  alloys,  a  perfect  die  will 
be  secured  from  moist  plaster  impressions  without  any  drying. 
As  the  bismuth  is  expansive  and  the  alloy  is  hard  and  some- 
what brittle,  I  run  only  a  thin  casting,  not  more  than  |  inch 
in  thickness,  over  the  highest  portion  of  the  impression,  I 
have  cast-iron  or  brass  heads  made  3^  inches  in  length,  3 
inches  in  diameter  at  large  end,  and  2  inches  at  the  other ;  the 
large  end  is  flat,  and  well  coated  with  common  tinman's  solder. 
This  head  is  heated  until  the  solder  begins  to  soften ;  it  is  then 
placed  in  a  pan  or  other  convenient  vessel,  and  the  die,  face 
side  up,  is  placed  upon  the  tinned  surface.  When  the  die 
begins  to  melt,  and  perfect  union  is  secured,  cold  water  is 
dashed  upon  the  die  and  head ;  and  thus  we  have  a  sharp 
die,  with  an  iron  head,  to  sustain  the  force  of  the  blow  in 
stamping  the  plate,  and  by  this  means  preventing  any  spread- 
ing of  the  face  of  the  die  or  liability  of  breaking  in  the  process" 
of  swaging. 

"  I  now  tjikc  sheet-lead  of  the  thicknc&s  of  about  No.  24, 
standard  gauge,  and  adapt  it  to  the  face  of  the  die  by  means 
of  a  wooden  mullet  or  burnisher,  or  other  convenient  means. 
Trim  the  lead  plate  to  the  size  required  for  the  plate  to  be 


134  MECHANICAL   DENTISTEY. 

stamped;  when  the  lead  plate  is  nicely  fitted^  remove  it  care- 
fully from  the  die  and  place  it  in  a  ring  or  narrow  moulding- 
flask,  the  palatal  side  up ;  now  gently  stamp  moulding-sand 
into  the  plate  and  flask  up  level  with  the  edges  of  the  flask  ; 
then  reverse  the  flask  and  cut  the  sand  away  dean  for  J  inch 
or  more  down  to  the  edge  of  the  lead  plate  all  around. 
Around  the  plate  place  a  common  moulding-ring  sufiiciently 
large  to  form  the  counter,  which  is  made  by  pouring  melted 
tin  or  lead  (or  any  alloys  of  these  metals)  on  to  the  lead  plate, 
being  careful  not  to  run  the  metal  so  hot  as  to  melt  the  lead 
plate.  When  the  counter  is  cool  enough  to  handle,  the  adher- 
ing sand  is  brushed  or  Avashed  away ;  the  die  is  then  placed 
into  the  bed  or  counter,  and,  with  a  moderate-sized  hammer, 
give  one  or  two  sharp  blows  to  bring  the  die  and  counter 
together.  In  swaging  gold  plates,  two  or  three,  or  more  dies 
may  be  required ;  these  may  be  made  either  by  running  the 
die-metal  into  the  impression  (if  not  broken)  or  by  running 
into  lead  plates,  gotten  up  as  before  described,  reserving,  of 
course,  the  first  die  and.  counter  for  the  final  swaging  of  the 
plate.  I  have  gotten  up  a  die  and  counter  from  the  impres- 
sion, with  the  aid  of  an  assistant,  in  the  foregoing  manner,  in 
twelve  minutes.  I  usually  get  out  my  die  immediately  after 
taking  the  impression ;  adapt  a  wax  or  gutta-percha  plate  to 
the  die,  and  get  the  articulation  before  the  patient  leaves  the 
ofiice." 

Dipping. — By  this  process  the  counter-die  is  first  obtained, 
and  from  this  the  die.  For  the  purpose,  two  or  three  sheet- 
iron  pans,  varying  in  size,  should  be  provided,  measuring  from 
three  to  five  inches  in  diameter  and  from  two  to  three  inches 
in  depth,  the  open  ends  of  which  should  be  somewhat  larger 
than  the  bottoms.  The  metal  for  the  counter  is  melted  and 
poured  into  the  pan,  and,  immediately  before  "  setting,"  the 
model,  being  unvarnished  and  previously  well  dried,  is  im- 
mersed, face  downward,  until  all  parts  of  the  palatal  arch  and 
ridge  are  imbedded  in  the  metal.  The  chamber,  as  well  as  the 
groove  around  the  outside  of  the  ridge  concerned  in  the  forma- 


METALLIC   DIES   AND    COUNTER-DIES.  135 

tion  of  a  rim  to  the  plate,  should,  in  this  ease,  be  formed  in 
plaster. 

Ordinarily,  the  conformation  of  the  ridge  above  and  below 
is  such  as  to  render  it  impracticable  to  remove  the  model  from 
the  metallic  matrix  without  injury;  hence  two  or  more  models 
will  be  required  whenever  this  method  is  practiced. 

After  the  counter-die  and  model  are  separated,  all  traces  of 
plaster  should  be  carefully  washed  from  the  matrix  and  the 
latter  surrounded  with  a  sheet-iron  ring;  forced  slie-htlv  into 
the  counter  immediately  outside  of  the  cavity  formed  by  the 
model ;  into  this  the  metal  for  the  die  is  poured,  filling  the 
matrix  and  ring. 

If  the  metal  or  alloy  forming  the  die  fuses  at  the  same  or  a 
higher  heat  than  that  composing  the  counter,  the  matrix  should 
be  protected  from  adhering  to  the  die  by  coating  its  surface 
uniformly  either  with  lamp-smoke  or  a  thin  mixture  of  whiting 
and  water  or  alcohol. 

Counter-die. — A  counter  to  the  die  is  generally  obtained 
directly  from  the  latter,  and  may  be  procured  in  either  of  two 
ways.  1.  The  die  is  placed,  face  upward,  upon  the  moulding- 
board,  and  sand,  prepared  as  in  moulding,  built  up  around  it, 
leaving  only  the  ridge  and  palatal  face  exposed.  It  is  then 
encircled  with  a  cast-  or  sheet-iron  ring  two  or  three  inches 
deep,  its  edge  imbedded  in  the  sand  to  prevent  the  escape  of 
the  fluid  metal ;  into  this  the  metal  for  the  counter  is  poured 
until  nearly  or  quite  full.  2.  The  metal  for  the  counter  may 
first  be  j)6ured  into  a  sheet-iron  vessel  of  proper  size,  and,  im- 
mediately before  setting,  the  face  of  the  die  is  immersed  in  the 
liquid  mass  and  held  perfectly  stationary  until  solidification  of 
the  counter  takes  place.  The  method  of  procuring  a  counter- 
die  directly  from  the  plaster  model,  as  in  the  process  of  dipping, 
has  already  been  described. 

The  metal  commonly  employed  for  the  counter  is  lead, 
although  other  substances,  as  tin,  type-metal,  some  of  the  more 
fusible  alloys  hereafter  to  be  mentioned,  etc.,  are  sometimes 
employed.  When  the  counter  is  taken  by  pouring  the  metal 
or  metals  composing  it  upon  a  die  fusing  at  a  low  heat,  some 


136  MECHANICAL   DENTISTRY. 

caution  should  be  observed  lest  the  two  pieces  adhere  by  par- 
tial fusion  of  the  die.  In  such  cases  the  surface  of  the  die 
should  be  well  protected  with  lamp-smoke  or  whiting;  the 
lead  should  be  poured  at  the  lowest  practicable  temperature, 
and  the  conduction  of  heat  facilitated  by  surrounding  the  die 
with  a  heavy  cast-iron  box  or  ring.  To  avoid  incurring  any 
risk,  however,  the  counter-die,  if  composed  of  a  less  fusible 
metal  or  compound  than  the  die,  may  be  first  obtained  directly 
from  the  model,  and  the  die  obtained  from  this,  as  in  the  pro- 
cess of  dipping ;  or,  a  counter  of  lead,  previously  taken  from 
a  zinc  or  other  more  infusible  die,  may  be  used. 

During  the  process  of  forcing  a  plate  into  adaptation  to  the 
form  of  the  mouth  with  swages,  it  not  unfrequently  happens 
that  the  marginal  portions  of  the  former  become  wedged  or 
immovably  fixed  between  the  outer  border  of  the  die  and  cor- 
responding portions  of  the  counter  before  its  central  portion  is 
forced  into  contact  with  the  palatal  surface  of  the  former,  thus 
rendering  it  difficult  to  conform  the  plate  accurately  to  the 
parts  without  the  application  of  sufficient  force  to  deface  or 
otherwise  mar  the  form  of  the  die.  In  such  cases  the  central 
portion  of  the  plate  may  be  first  swaged  with  a  partial  counter, 
which  is  made  to  receive  only  the  palatal  portion  and  upper 
surface  of  the  ridge  of  the  die.  After  forcing  the  central  part  of 
the  plate  into  adaptation  with  the  partial  counter,  the  process 
may  afterwards  be  completed  with  a  full  counter  after  having 
turned  the  edges  of  the  plate  down  upon  the  outer  border  of 
the  ridge  with  a  mallet  and  pliers. 

As  before  remarked,  preference  is  usually  given  to  lead  in 
the  formation  of  a  counter-die,  mainly  on  account  of  its  greater 
softness.  This  property  in  a  counter  is  practically  important. 
In  the  process  of  forcing  a  metallic  plate  into  adaptation  to  the 
mouth,  partial  displacement  or  yielding  of  either  the  die  or 
counter,  or  of  both,  necessarily  occurs,  and  it  is  scarcely  neces- 
sary to  remark  that  whatever  change  of  form  is  produced 
should  take  place  wholly  in  the  counter,  otherwise  deformity 
of  the  die  must  ensue. 

Essential  Properties  of  a  Die. — There  are  certain  properties 


METALLIC  DIES   AND   COUXTER-DIES.  137 

which  it  is  indispensable  that  a  metallic  die  should  possess 
more  or  less  perfectly  in  order  to  answer  fully  the  requirements 
of  the  dentist. 

1.  A  die  should  be  sufficiently  hard  to  resist  any  necessary 
force  applied  to  it  in  stamping  the  plate  without  suifering  any 
material  change  in  the  form  of  its  face,  by  which  latter  term 
is  meant  that  portion  of  the  die  with  which  the  plate  is  brought 
into  contact.  This  property  is  most  indispensable  in  those 
cases  where  the  arch  of  the  mouth  is  very  deep,  the  ruga  promi- 
nent and  sharply  defined,  and  where  the  alveolar  ridge  is 
marked  by  angular  and  abrupt  prominences  and  depressions. 
In  such  cases,  if  the  die  is  not  sufficiently  resistant,  the  points 
most  prominent  upon  its  face  will  be  bruised  or  battered  down, 
while  the  plate  will  fail  to  be  forced  perfectly  into  the  cavities 
or  depressions,  and  its  coaptation  to  the  mouth,  to  that  extent, 
rendered  faulty.  The  cases  in  which  a  less  degree  of  hardness 
is  admissible  is  where  the  arch  of  the  mouth  is  broad  and  shal- 
low, the  ruga  imperfectly  defined,  and  the  ridge  regular  and 
symmetrical.  The  conformation  of  the  mouth,  therefore,  will, 
in  respect  to  the  property  of  hardness,  admit  of  some  latitude 
in  the  choice  of  the  metal  or  alloy  employed  in  the  formation 
of  a  die. 

2.  Another  important  property  of  a  metallic  die  is  non- 
cojitraction,  so  far,  at  least,  as  this  is  attainable.  Inasmuch  as 
the  successful  adaptation  of  the  plate  depends,  in  a  great 
measure,  upon  an  accurate  representation  of  the  precise  form 
of  the  mouth  in  the  die,  it  is  of  the  first  importance  that  the 
latter,  other  essential  requisites  being  secured,  should  be  com- 
posed of  some  metal  or  metals  having  the  least  possible  con- 
traction in  cooling.  Contraction  is,  in  varying  degrees,  common 
to  all  metals  exposed  to  a  decreasing  temperature,  and  it  is 
impossible,  therefore,  to  obtain  a  perfectly  faultless  co])y  of  the 
mouth  in  metal.  Fortunately,  as  well  for  the  expert  as  the 
unskilled  manipulator,  the  unavoidable  shrinkage  incurred  is 
partially  or  wholly  compensated  for  by  the  expansion  of  the 
plaster  and  the  yielding  condition  of  the  soft  tissues  of  the 
month,  but  under  no  circumstances  should  the  accommodation 


138  MECHANICAL   DENTISTEY. 

aiforded  by  the  condition  last  mentioned  encourage  negligence 
or  unskilfulness  in  the  use  of  all  available  means  necessary  to 
secure  the  most  accurate  adaptation  of  the  base.  Ordinarily, 
a  moderate  degree  of  contraction  will  not  materially  impair 
the  fit  of  a  plate ;  on  the  contrary,  in  the  case  of  the  upper 
jaw,  it  sometimes  favors  its  adhesion  and  retention  in  the 
mouth.  Cases,  on  the  other  hand,  frequently  occur  where 
the  least  practicable  amount  of  shrinkage,  even  at  the  partial 
sacrifice  of  other  properties,  becomes  indispensable  in  the  die. 

3.  A  third  important  requisite  of  a  die  is  fusibility.  Aside 
from  the  convenience  incident  to  the  use  of  metals  which  fuse 
at  a  low  heat,  there  is  another  consideration  favoring  this  prop- 
erty of  more  practical  importance.  It  is  well  known  that  all 
metals  expand  by  heat  and  contract  by  cold.  In  obedience  to 
this  law,  metals  fusing  at  a  high  heat  suffer  a  greater  aggregate 
contraction  than  those  melting  at  a  lower  temperature,  and,  as 
between  two  metallic  bodies  of  equal  dimensions,  liquefying  at 
different  temperatures,  the  difference  in  contraction  will  corre- 
spond exactly  with  the  difference  in  the  number  of  degrees 
through  which  each  passes  from  the  point  of  solidification  to 
the  mean  temperature  of  the  air,  allowance  being  made  for  the 
difference  in  their  ratios  of  contraction.  Two  dies,  one  com- 
posed of  copper  and  the  other  of  zinc,  will  serve  to  illustrate. 
Fused  copper  solidifies  at  1900°.  lu  cooling,  therefore,  it 
contracts  through  over  1800°  to  reach  a  working  temperature, 
while  zinc,  fusing  at  773°,  contracts  through  only  about  700° 
to  reach  the  same  temperature.  As  before  stated,  the  difference 
in  the  contraction  of  metals  will  be  somewhat  modified  by  that 
in  their  ratio  of  contraction,  but  it  will  always  be  found  that 
the  more  fusible  metals  have  the  least  aggregate  shrinkage 
whenever  any  considerable  disparity  exists  between  their  fusing- 
points.  It  is  in  accordance  with  the  principles  here  set  forth 
that  the  more  fusible  alloys,  some  of  which  melt  at  remarkably 
low  temperatures,  are  employed  whenever  it  is  important  to 
obtain  a  die  as  nearly  the  exact  counterpart  of  the  model  as 
possible. 

4.  Finally,  a  die  should  be  sufficiently  cohesive  to  resist  the 


METALLIC   DIES    AND    COUNTER-DIES.  139 

repeated  blows  of  a  heavy  hammer  without  parting  or  crack- 
ing. Many  metals,  as  aiitimony,  bismuth,  etc.,  in  other  re- 
spects suitable  for  dies,  are  objectionable  on  account  of  brittle- 
ness.  But  it  must  not,  therefore,  be  inferred  that  all  metals 
that  are  denominated  brittle  are  inadmissible  for  this  purpose ; 
for  zinc,  which,  in  its  ordinary  condition,  is  ranked  as  a  brittle 
metal,  and  type-metal,  which  is  always  so,  are  in  no  danger  of 
being  forced  asunder  or  of  suffering  displacement  when  in  the 
compact  form  of  a  die,  provided  the  force  used  in  swaging  is 
judiciously  applied  or  proper  form  and  sufficient  depth  are 
given  to  the  body  of  the  die. 

To  recapitulate  briefly :  a  die  should  be  formed  of  some 
metal  or  alloy  that  has  a  surface  hardness  sufficient  to  resist 
compression ;  that  fuses  at  a  low  temperature ;  that  does  not, 
in  any  material  degree,  contract  in  the  act  of  cooling;  and 
whose  particles  adhere  with  sufficient  cohesive  force  to  main- 
tain perfectly  its  integrity  of  form  under  the  hammer.  Any 
one  or  two  of  these  properties  are  readily  attainable  in  the  same 
die,  but  no  one  known  metal  or  alloy  combines  all  of  them  per- 
fectly. Thus  either  cast  iron,  brass,  bronze,  or  cannon-metal 
Avould  form  an  excellent  material  in  respect  to  surface  hardness, 
and  in  the  compact  form  of  a  die,  would  be  sufficiently  cohe- 
sive, but  few  enjoy  convenient  facilities  for  melting  them ;  be- 
sides, their  great  contraction  consequent  upon  their  high  fusing- 
point  would  render  their  employment  entirely  inadmissible. 
Again,  certain  alloys,  as  those  composed  of  lead,  tin,  and  anti- 
mony or  bismuth,  are  eminently  suitable  on  account  of  their 
extreme  fusibility  and  comparative  exemption  from  shrinkage, 
but  they  gain  these  properties  at  the  expense  of  that  degree  of 
hardness  necessary  to  resist  compression.  Tin  in  its  uncom- 
bined  state  is  ordinarily  sufficiently  fusible,  tenacious,  and  non- 
contraetile,  but  is  too  soft  and  yielding  when  forcibly  com- 
pressed. Antimony  and  bismuth  are  sufficiently  hard,  fusible, 
and  non-contractile,  but  are  objectionable  on  the  score  of  ex- 
treme brittleness. 

Any  metallic  substance  that  combines  most  perfectly  the 
several  properties  referred  to  is,  therefore,  best  adapted  to  the 


140  MECHANICAL   DENTISTEY. 

necessities  of  the  mechanical  operator,  and  experience  has  uni- 
versally accorded  pre-eminence  in  this  respect  to  zinc.  It  pre- 
sents a  more  resistant  surface  to  the  blow  of  a  hammer  than 
either  copper  or  brass,  three  times  more  so  than  that  of  tin,  and 
more  than  double  that  of  type-metal.  As  it  usually  occurs  in 
commerce  it  may  be  classed  as  a  brittle  metal,  but  when  an- 
nealed it  is  tough  and  malleable.  It  melts  at  a  heat  (773°) 
which  may  be  readily  commanded,  and  contracts  but  little  in 
cooling.  The  late  Professor  Austen  demonstrated  by  actual 
experiments  that  an  average-sized  zinc  die,  measuring  two 
inches  transversely,  contracts  27-lOOOths  of  an  inch  from  out- 
vside  to  outside  of  the  alveolar  ridge,  being  equivalent  in  thick- 
ness to  three  ordinary  leaves  of  a  journal.  Professor  Austen 
remarks :  "  In  the  first  case  (upper  jaw)  the  plate  would  '  bind,' 
and  if  the  ridge  were  covered  by  an  unyielding  mucous  mem- 
brane, it  would  prevent  accuracy  of  adaptation.  In  the  second 
case  (under  jaw)  the  plate  would  have  too  much  lateral  ^play,' 
and  consequently  lack  stability.  Again,  in  a  moderately  deep 
arch,  say  a  half  inch  in  depth,  the  shrinkage  between  the  level 
of  the  ridge  and  the  floor  of  the  palate  will  be  nearly  7-lOOOths 
— rather  more  than  one  leaf  of  the  journal.  In  the  deepest 
arches  this  shrinkage  becomes  a  serious  difficulty ;  in  the  shal- 
lower cases  it  is  not  of  much  moment,  as  there  is  no  mouth  so 
hard  as  not  to  yield  the  1  or  2-lOOOths  of  an  inch." 

As  before  stated,  a  moderate  degree  of  shrinkage  in  the  die 
may,  in  certain  conditions  of  the  mouth,  practically  favor  the 
adhesion  and  permanent  retention  of  a  plate  applied  to  the 
upper  jaw.  The  conditions  alluded  to,  and  which  prevail  in  a 
greater  or  less  degree  in  all  cases,  are  soft  and  yielding  ridge 
and  comparatively  hard  and  unimpressible  palate.  Now,  if  in 
the  first  instance  the  plate  is  swaged  into  uniform  contact  with 
all  parts  of  the  jaw,  it  will  be  readily  perceived  that  if  pressure 
is  made  over  the  ridge  on  one  side  the  latter  will  yield,  while 
the  central  portion  of  the  plate,  meeting  with  a  fixed  point  of 
resistance  at  the  floor  of  the  palate,  will  "ride"  upon  the  latter, 
and  thus  throw  the  plate  from  the  ridge  on  the  opposite  side 
of  the  jaw.     If,  however,  a  space  equal  to  one  or  two  thick- 


METALLIC    DIES    AND    COUXTER-DIES.  141 

nesses  of  the  plate  exists  between  the  latter  and  the  roof  of  the 
mouth,  as  a  consequence  of  contraction  in  the  die,  the  plate,  as 
it  is  carried  against  the  palate,  in  the  act  of  exhausting  the  air 
from  beneath  it,  will  at  the  same  time  forcibly  compress  the 
ridge,  securing  thereby  a  more  resistant  basis  along  the  border, 
and  providing  more  certainly  against  displacement  of  the  base 
on  the  application  of  forces  brought  to  bear  upon  it  in  masti- 
cation. 

The  extent  to  which  the  shrinkage  of  a  die  may  be  admitted 
in  any  given  case,  will  depend  partly  upon  difference  in  the 
conditions  heretofore  mentioned  in  the  soft  parts  of  the  mouth, 
and  in  part,  also,  upon  the  general  configuration  of  the  jaw. 
In  a  medium-sized  mouth,  with  a  depth  of  say  half  an  inch  to 
the  arch,  a  moderately  soft  ridge  and  resisting  palate,  the 
shrinkage  incident  to  zinc  will  be  unimportant,  and  in  many 
cases  will  be  advantageous.  If,  however,  the  vault  is  very 
deep,  even  though  there  be  a  yielding  ridge,  the  unavoidable 
contraction  of  a  zinc  die  will  throw  the  plate  so  far  from  the 
arch  as  to  render  it  difficult  for  the  patient  to  exhaust  the 
atmosphere  from  between  it  and  the  floor  of  the  palate,  and 
even  when  the  latter  is  practicable,  the  plate  will  bind  with 
such  force  upon  the  outer  border  of  the  ridge  as  not  only  to 
produce  pain  and  irritation  of  the  compressed  parts,  but  the 
resistance  afforded  at  these  points  will  be  sufficient,  in  many 
cases,  to  break  up  the  adhesion  and  force  the  plate  from  the 
palate.  Again,  as  an  extreme  case,  if  the  ridge  and  palate  are 
somewhat  uniformly  unyielding,  and  the  palatal  vault  is,  at 
the  same  time,  very  deep,  a  zinc  die  can  only  be  made  avail- 
able in  bringing  the  base  as  nearly  into  adaptation  as  possible, 
after  which  the  operation  may  be  completed  with  a  swage  hav- 
ing a  less  degree  of  shrinkage,  and  which,  as  a  mere  finishing 
die,  need  not  necessarily  be  so  hard  as  zinc. 

In  conforming  a  plate  to  the  lower  jaw,  the  die  should  be 
as  free  as  possible  from  contraction  in  all  cases.  The  greatest 
shrinkage  in  such  cases  will  be  between  the  posterior  extremi- 
ties of  the  ridge,  giving  too  much  lateral  play  to  the  plate ;  in 
addition  to  which  the  posterior  and  inner  edge  of  the  base, 


142  MECHANICAL,   DENTISTRY. 

projecting  out  from  the  ridge,  will  obstruct  the  free  action  of 
the  tongue,  Avhile  the  latter  will  tend  to  lift  it  from  the  ridge 
and  render  it  unstable.  These  conditions  may  be  partially- 
remedied  by  turning  the  eclgQ  of  the  plate  in  against  the  ridge 
with  pliers ;  but  this  expedient  should  never  be  resorted  to  in 
any  case  whenever  it  is  practicable  to  secure  a  correct  adapta- 
tion by  swaging. 

In  all  cases  in  which  a  zinc  die  fails  to  bring  the  plate  into 
proper  adaptation  to  the  parts,  either  of  the  following  metallic 
compounds  may  be  used  to  complete  the  process  after  partial 
stamping  with  zinc. 

Type-Metal. — Lead,  5  parts ;  antimony,  1  part.  Fuses  at 
500°  ;  contraction  less  than  one-half  that  of  zinc ;  more  com- 
pressible than  the  latter,  and  very  brittle. 

Babbitt,  or  Anti-fridion  3Ietal. — Copper,  3  parts ;  antimony, 
1  part ;  tin,  3  parts.  First  fuse  the  copper,  and  then  add  the 
antimony  and  tin.  Melts  at  a  moderately  low  heat;  contracts 
but  little ;  is  brittle,  but  may  be  rendered  less  so  by  adding 
tin. 

Zinc,  4  parts ;  tin,  1  part.  Fuses  at  a  lower  heat,  contracts 
less  in  cooling,  and  has  a  less  surface  hardness  than  zinc. 

Tin,  5  parts ;  antimony,  1  part.  Melts  at  a  lower  heat  than 
either  of  the  preceding  alloys;  contracts  but  slightly  in  cool- 
ing ;  is  harder  than  tin,  and  sufficiently  cohesive.  It  is  readily 
oxidized,  and  should  be  poured  as  soon  as  melted. 

Fusible  Alloys. — The  following  tabular  view  of  the  more 
fusible  alloys,  the  respective  properties  of  which  are  deduced 
from  actual  experiments,  was  given  by  Professor  Austen,  in  a 
paper  on  "  Metallic  Dies."*  Zinc  is  introduced  into  the  table 
for  the  purpose  of  comparison. 

*  American  Journal  of  Dental  Science,  vol.  vi,  p.  367. 


METALLIC   DIES    AXD    COUNTEE-DIES. 


143 


1.  Zinc 

2.  Lead,  2,  Tin,  1 

3.  Lead,  1,  Tin,  2 

4.  Lead,  2,  Tin,  3,  Antimony,  1 

5.  Lead,  5,  Tin,  6,  Antimony,  1 

6.  Lead,  5,  Tin,  6,  Antimony,  1  Bismuth,  3... 

7.  Lead,  1,  Tin,  1,  Bismuth,  1 

8.  Lead,o,  Tin,  3,  Bismuth,  8 

9.  Lead,  2.  Tin,  1,  Bismuth,  3 


Melting 

Contrac- 

Hard- 

Brittle- 

point. 

tility. 

ness. 

ness. 

770° 

.013fi6 

.018 

5 

440° 

.00033 

.050 

3 

340" 

.OOSOO 

.040 

3 

420° 

.00433 

.026 

7 

320° 

.00566 

.035 

6 

300° 

.00266 

.030 

9 

250° 

.00066 

.042 

7 

200° 

.00200 

.045 

8 

200° 

.00133 

.048 

7 

Professor  A.,  in  commenting  on  the  preceding  table,  ob- 
serves :  "  The  last  column  contains  an  approximate  estimate  of 
the  relative  brittleness  of  the  samples  given.  As  in  the  other 
columns,  the  low  numbers  represent  the  metals,  so  far  as  this 
property  is  concerned,  most  desirable.  Those  marked  below 
5  are  malleable  metals ;  those  above  5  are  brittle ;  zinc, 
marked  5,  separates  these  two  classes,  and  belongs  to  one  or 
the  other,  according  to  the  way  in  which  it  is  managed."  Allu- 
sion is  here  made  to  the  process  of  annealing  zinc,  and  which 
has  already  been  adverted  to  when  considering  the  latter  metal 
in  the  former  part  of  the  work.  The  special  method  employed 
is  thus  described  by  the  author  already  quoted.  "  The  simplest 
way  to  anneal  a  zinc  die  is  to  place  it  in  the  melting  ladle 
with  about  a  tablespoonful  of  water,  removing  it  in  thirty 
seconds  after  the  water  has  boiled  away.  If  the  fire  is  a  very 
hot  one,  remove  it  immediately  on  the  disappearance  of  the 
water.  It  will  often  happen  that  the  die  is  annealed  in  the 
process  of  taking  the  counter-die.  This  will  more  certainly 
occur  when  Nos.  7,  8,  or  9  (see  table),  are  used  for  the  counter. 
For  example,  take  tin,  using  a  mass  twice  the  size  of  the  die, 
should  it  be  heated  to  540°  (100°  above  melting-point),  it 
would  not,  allowing  for  loss  of  heat  by  radiation  and  contact 
with  the  cast-iron  ring  (if  one  be  used),  heat  the  zinc  beyond 
330°.  Lead,  cast  as  cool  as  it  could  possibly  be  poured,  unless 
in  a  very  heavy  ring  (such  as  a  'cart-wheel  box'),  or  in  quantity 
too  small  for  a  well-shaped  crmnter,  would  be  apt  to  raise  the 
zinc  at  least  to  400°,  and  so  impair  its  malleability,  whilst,  if 


144  MECHANICAL    DENTISTRY. 

poured  as  hot  as  many  are  in  the  habit  of  doing,  the  zinc  will 
remain  as  brittle  as  when  first  cast."* 

*  To  Professor  P.  H.  Austen,  whose  various  contributions  relating  to  the 
mechanical  department  of  practical  dentistry  have  done  much  to  unfold  and 
elucidate  the  principles  involved  in  the  practice  of  this  important  specialty, 
the  author  would  acknowledge  his  indebtedness  for  many  of  the  valuable 
data  and  practical  suggestions  that  may  be  found  embodied  in  the  foregoing 
chapter ;  and,  had  not  the  limited  space  assigned  us  compelled  a  condensa- 
tion of  his  views  on  the  subject  of  metallic  dies  and  counters,  we  might 
have  done  the  reader  an  essential  service  by  transferring  to  our  pages  many 
of  his  eminently  practical  observations  on  the  subject  entire. 


PIVOTING   ARTIFICIAL   CROWNS.  145 


CHAPTER  Y. 

Partial   Dentures. 

The  almost  unlimited  modifications  in  the  form  of  substi- 
tutes designed  to  supply  the  loss  of  a  portion  only  of  the 
natural  teeth,  and  the  difficulties  oftentimes  incident  to  a  har- 
monious arrangement  of  the  teeth  of  replacement,  as  well, 
also,  as  the  impracticability  of  always  securing  a  perfectly 
satisfactory  and  efficient  antagonism  or  closure  of  the  artificial 
with  the  natural  organs,  frequently  surround  this  process  with 
peculiar  embarrassments,  and  often  render  their  successful 
application  extremely  difficult.  They  will,  accordingly,  be 
found  to  demand  of  the  operator  the  exercise  of  greater  skill, 
ingenuity,  and  discrimination  than  are  usually  required  of  him 
in  the  construction  and  application  of  entire  dentures. 

The  various  means  employed  in  fixing  or  retaining  partial 
sets  of  teeth  in  the  mouth  will  be  first  considered.  Either  of 
the  following  methods  may  be  adopted  according  to  the  pref- 
erences of  the  operator,  or  the  requirements  of  individual  cases. 

1.  'Pivoting  an  ariifieial  crown  to  the  root  of  a  natural  tooth. 

2.  Clamping  to  the  natural  teeth.  3.  Wood  pivots  adjusted  to 
tubed  plates.  4.  Pivoting  plate  to  the  7'oots  of  the  natural  teeth. 
5.  Atmospheric  pressure. 

PIVOTING    artificial   CROWNS. 

The  process  of  pivoting  or  grafting  an  artificial  crown  upon 
the  root  of  a  natural  tooth  has  been  long  practiced,  and,  when 
skilfully  performed  with  intelligent  views  of  the  various  con- 
ditions which  recommend  and  justify  the  operation,  affi)rds 
a  valuable  and  unobjectionable  means  of  substitution.  The 
success  of  the  operation  will  be  greatly  modified  by  the  follow- 
ing circumstances : 

10 


146  MECHANICAL   DENTISTRY. 

1.  The  Condition  of  the  Root,  its  Appendages,  and  Sur- 
rounding Structures. — If  the  root  to  be  pivoted  is  strong,  well 
formed  and  securely  attached  to  the  jaw,  a  living,  healthy- 
pulp  present,  and  the  peridental  membrane  free  from  disease, 
the  operation  will  be  attended,  in  a  large  preponderance  of 
cases,  with  the  happiest  results,  and  in  respect  to  utility,  com- 
fort, and  appearance,  is  superior  to  any  other  mode  of  substi- 
tution. If,  however,  the  pulp  of  the  tooth  has  been  previously 
destroyed  by  disease,  and  inflammation  and  suppuration  of  the 
adjacent  tissues  have  supervened,  the  probabilities  of  complete 
success  will  be  somewhat  modified ;  for  although  these  latter 
conditions  may  ordinarily  be  subdued  by  appropriate  treat- 
ment, yet  that  a  latent  predisposition  favoring  their  recurrence 
exists  is  manifested  by  the  unfavorable  results  which  sometimes 
follow  the  operation  of  pivoting  under  apparently  favorable 
circumstances. 

In  no  case,  we  are  convinced,  unless  under  circumstances  of 
peculiar  exigency,  should  an  artificial  crown  be  attached  to  a 
root  whenever  the  latter  is  complicated  with  incurable  disease 
of  the  investing  membrane  or  alveolar  abscess.  It  may  be 
safely  affirmed  that  the  failures  so  common  to  this  method,  and 
the  consequent  disrepute  into  which  it  has  deservedly  fallen,  as 
ordinarily  performed,  is  fairly  chargeable  not  so  much  to  un- 
skilful manipulation  as  to  a  want  of  proper  appreciation  of 
the  pathological  conditions  which  clearly  contraindicate  its  em- 
ployment. The  facilities  enjoyed  by  the  dentist  of  the  present 
day  in  the  employment  of  the  various  approved  methods  of 
replacement,  other  than  the  one  under  consideration,  no  longer 
make  it  either  necessary  or  pardonable  to  subject  the  patient  to 
a  course  of  treatment  which  unavoidably  necessitates  a  per- 
petual drainage  of  depraved  and  offensive  pus  either  through 
fistulous  openings  in  the  gum  or  through  channels  provided  by 
art. 

As  respects  the  surrounding  structures,  it  is  well,  with  a 
view  of  removing  any  disturbing  causes,  to  institute  a  careful 
examination  of  the  mouth  before  inserting  pivot  teeth,  and  if 
any  of  the  remaining  teeth  are  found  carious  or  incrusted  with 


PIVOTING    ARTIFICIAL    CROWNS.  147 

tartar,  or  the  mucous  membrane  and  gums  are  inflamed  or 
otherwise  diseased,  they  should  be  treated  in  accordance  with 
the  indications  furnished  by  the  particular  morbid  conditions 
present. 

2.  Dic(the8is  of  the  Patient. — Cases  frequently  occur  where 
there  exists  a  marked  constitutional  predisposition  to  inflam- 
mation, and  where,  from  the  operation  of  very  slight  causes, 
injuries  inflicted  upon  any  portion  of  the  body  tend  to  termi- 
nate in  suppuration  of  the  tissues  involved.  Whenever  this 
predisposition  exists  in  any  marked  degree,  the  operation, 
though  other  conditions  may  favor  success,  is  liable  at  all  times 
to  terminate  unfavorably,  and,  therefore,  if  performed  at  all,  it 
should  be  done  in  the  most  careful  manner  and  only  under 
circumstances  that  promise  the  best  chances  of  success.  In 
such  cases  not  more  than  one  tooth  should  be  inserted  at  a 
single  sitting,  and  it  will  be  prudent,  in  many  cases,  after  hav- 
ing prepared  the  root,  to  defer  the  completion  of  the  operation 
for  a  few  days,  or  to  adjust  a  tooth  temporarily  with  a  pivot 
loosely  fitted,  until  the  irritation,  unavoidably  produced  by 
filing,  drilling,  etc.,  has  completely  subsided. 

3.  Manner  of  Performing  the  Operation. — The  healthy  con- 
dition of  the  root  and  contiguous  parts,  and  the  ultimate  utility 
of  the  substitute,  may  be  very  materially  prejudiced  by  care- 
less, hurried,  or  injudicious  manipulation;  as  where  the  re- 
maining portions  of  the  natural  crowns  of  the  tooth  are  vio- 
lently removed  with  excising  forceps,  or  by  the  unskilful  use 
of  files  in  dressing-  the  root,  or  drills  in  enlarg-ino;  the  central 
cavity,  or  by  undue  or  misapplied  force  in  the  final  adjustment 
of  the  artificial  crown,  or  finally,  by  a  faulty  position  of  the 
tooth  of  replacement  by  which  the  root  is  subjected  to  injurious 
strain  either  by  lateral  pressure  or  premature  closure  against 
those  of  the  opposite  jaw.  By  the  operation  of  either  or  all  of 
these  causes,  disease  of  a  more  or  less  intractable  character 
may  be  induced  which  will  impair  the  usefulness  of  the  arti- 
ficial organ  and  subject  the  patient  to  much  present  and  future 
distress  and  annoyance. 

Preparation  of  the  Root. — In  the  process  of  preparing  the 


148 


MECHANICAL   DENTISTEY. 


root  for  the  attachment  of  an  artificial  tooth,  all  remaining 
portions  of  the  natural  crown  should  first  be  removed  with 
suitable  instruments.  If  the  cervical  portion  of  the  tooth  is 
comparatively  sound  and  unbroken  this  may  be  most  expedi- 
tiously accomplished,  and  with  less  risk  of  injury  to  the  root, 
by  employing  a  very  fine  saw  attached  to  a  steel  frame  or  car- 
rier, as  shown  in  Fig.  42.     The  saw  should  be  narrow  enough 

Fig.  42. 


to  enable  it  to  take  a  curvilinear  direction  in  cutting;,  as  this 
will  enable  the  operator  to  separate  the  crown  nearly  or  quite 
on  a  line  with  the  arched  margin  of  the  gum,  thus  dispensing, 
in  a  great  measure,  with  the  use  of  other  instruments  in  the  final 
dressing  of  the  cut  end  of  the  root. 

The  saw  should  be  passed  along  the  side  of  the  tooth  to  the 
gum,  and  the  crown  separated  either  by  cutting  directly  across 
to  the  opposite  side,  or  as  nearly  on  a  line  with  the  curvature 
of  the  anterior  and  posterior  margins  of  the  gum  as  possible 
without  wounding  the  latter.  During  the  operation  the  saw 
should  be  kept  constantly  wet,  and  the  crown  should  be  sup- 
ported by  the  fingers. 

If  the  remains  of  the  crown  are  friable,  or  if  they  consist  of 
but  fragmentary  portions  of  enamel,  they  may  be  readily  cut 

Fig.  43. 


^^  -"'"^vr^ 


away  with  excising  forceps,  two  forms  of  wmS^re  exhibited 
in  Fig.  43.     The  one  having  square,  transverse  cutting-edges, 


PIVOTING   ARTIFICIAL   CROWXS.  149 

closing  at  right  angles  with  the  shaft  is  generally  employed. 
Serious,  if  not  irreparable,  injury  may  be  inflicted  by  the  care- 
less or  unskilful  use  of  this  instrument,  either  by  producing  so 
violent  a  concussion  as  to  induce,  in  some  instances,  incurable 
disease  or  absolute  necrosis  of  the  root;  or  by  fracturing  the 
latter  in  such  a  way  as  to  unfit  it  for  the  reception  of  the  pivot- 
crown.  The  forceps,  therefore,  should  never  be  used  to  excise 
the  crown  with  a  single  cut  whenever  any  considerable  portion 
of  the  root  at  the  gum  remains  unaffected  by  disease,  and  even 
when  the  latter  is  friable  or  partially  destroyed  by  decay,  they 
should  be  used  with  great  caution,  cutting  or  chipping  away 
small  portions  at  a  time  until  as  much  of  its  substance  is  re- 
moved as  is  practicable  with  the  forceps. 

After  the  use  of  the  saw  or  excising  forceps,  any  remaining 
portions  projecting  beyond  the  free  margins  of  the  gum  should 
then  be  removed  and  proper  shape  given  to  the  end  of  the 
root.  A  half-oval  file,  with  a  sharp  and  tolerably  fine  cut 
running  obliquely  across  its  convex  surface,  or  suitably  formed 
corundum  burrs  or  disks  are  the  best  for  the  purpose,  and,  when 
in  use,  should  be  kept  constantly  wet  and  free  from  clogging 
particles  of  bone.  The  end  of  the  root  should  be  dressed  down, 
anteriorly,  at  least,  a  little  below  the  free  margin  of  the  gum, 
care  being  taken  not  to  lacerate  its  peridental  attachment ;  in 
this  way  the  artificial  crown,  when  adjusted  to  the  root,  will 
unite  so  intimately  with  the  gum  in  front  as  to  render  exposure 
impossible.  The  surface  of  the  root,  prepared  in  this  manner, 
will  present  a  concavity  corresponding  with  the  festoon  of  the 
gum. 

If  a  living  pulp  remains  in  the  root,  it  will  not  ordinarily 
be  j)racticable,  unless  there  is  partial  obliteration  and  conse- 
quent recession  of  the  pulp-cavity  as  the  result  of  ossific  de- 
posits, either  to  saw  off  the  root  on  a  line  with  the  gum,  or 
even  transversely,  or  to  dress  the  root  even  with  the  gum,  with- 
out inflicting  insuflerablepain.  It  will  be  necessary,  therefore, 
either  to  extirpate  the  ])ulp  through  the  carious  opening  in  the 
crown  before  the  latter  is  removed,  or,  if  not  exposed  by  the 


150 


MECHANICAL  DENTISTEY. 


operation  of  sawing  or  filing,  through  an  opening  into  the  pulp 
made  with  a  drill  or  cutting  instrument  after  excision. 

Arsenic  may  be  employed  for  the  purpose  of  devitalizing 
the  pulp  preparatory  to  its  removal,  or  its  extirpation  may  be 
effected  by  direct  operation  with  suitable  instruments.  By 
the  latter  method  the  vitality  of  the  root,  through  its  peri- 
dental circulation,  will  be  better  preserved.  Its  extirpation 
may  generally  be  readily  effected  with  the  use  of  a  three  or 
four-sided,  barbed,  untempered  broach,  which,  being  small 
enough  to  penetrate  freely  to  the  apex  of  the  root,  is  thrust 
quickly  to  the  bottom  of  the  canal,  rotated,  and  withdrawn ; 
when,  if  the  entire  pulp  does  not  come  away  adherent  to  the 
broach,  the  operation  may  be  repeated,  with  comparatively 
little  pain,  until  all  portions  of  it  are  removed. 

After  the  removal  of  the  pulp,  the  apical  foramen  should  be 
thoroughly  closed  by  any  method  usually  employed  in  root- 
filling.  A  neglect  of  this  important  measure  will  greatly  en- 
danger the  success  of  the  operation. 

The  proper  treatment  and  preparation  of  the  root  having 
been  thus  far  accomplished,  the  canal  of  the  latter  should  next 


Fig.  44. 


4 


be  enlarged  for  the  reception  of  a  pivot.  This  is  effected  with 
a  suitable  broach  or  with  drills  of  various  forms.  When  the 
canal  presents  the  form  of  a  cleft  or  fissure,  a  spherical  or  cone- 
shaped  burr-drill  should  be  used ;  if,  however,  the  pulp-cavity 
approaches  a  cylindrical  form,  the  operation  will  be  more 
speedily  performed  with  a  four-sided  broach,  or,  what  is  still 
better,  a  spear-pointed  or  spiral  drill,  all  of  which  are  exhibited 
in  Fig.  44.     The  natural  opening  in  the  root  should  be  en- 


PIVOTING   ARTIFICIAL   CROWNS.  151 

Jarged  to  the  depth  of  from  one  and  a  half  to  two  or  more 
lines,  according  to  the  length  of  the  root ;  and  the  orifice  should 
be  made  large  enough  to  admit  a  pivot  of  sufficient  size  to 
secure  the  crown  firndy  in  position.  The  direction  of  the  drill 
in  cutting  should  follow  closely  that  of  the  natural  canal  in 
the  root,  since  but  a  slight  deviation  in  this  respect  may  en- 
danger the  integrity  ot  the  latter  by  too  great  a  thinning,  or 
actual  perforation,  of  its  walls.  In  all  cases,  however,  where 
the  direction  of  the  canal  will  admit  of  it,  the  shaft  of  the  in- 
strument should  be  held  steadily  on  a  line  with  the  circle 
formed  by  the  cutting  edges  of  the  adjoining  teeth,  and  either 
equidistant  between  the  latter  or  with  such  a  lateral  inclina- 
tion as  will  give  to  the  tooth  of  replacement  a  symmetrical 
arrangement  in  the  arch.  During  the  operation,  the  drill 
should  be  kept  constantly  wet,  and  loose  particles  of  bone 
should  be  washed  from  the  cavity  by  occasional  injections  of 
water. 

Fitting  the  Crown. — The  pivot  crown  selected  for  any  given 
case  should  correspond,  as  nearly  as  possible,  in  size  and  gen- 
eral configuration  with  its  fellow  of  the  opposite  side,  or,  where 
sev^eral  are  inserted,  with  the  form  and  size  of  the  natural 
organs  which  they  represent.  The  tooth  or  teeth  of  replace- 
ment should  also  harmonize  in  color  with  those  immediately 
adjoining.  The  cervical  portion  of  the  crown  applied  to  the 
root  should  correspond,  as  nearly  as  possible,  in  dimensions 
with  the  filed  surface  of  the  root,  and  the  adaptation  of  the 
two  surfaces  should  be  sufficiently  accurate  at  all  points  to  affijrd 
a  firm  basis  for  the  crown,  and,  at  the  same  time,  to  exclude 
perfectly  all  particles  of  alimentary  or  other  solid  substances, 
the  decomposition  of  which  would  tend  to  the  decay  or  disease 
of  the  root,  or  become  oifensive  in  the  mouth.  To  secure  such 
a  coaptation  of  the  articulating  surfaces,  more  or  less  dressing 
of  the  root  and  grinding  from  the  base  of  the  crown  will  be 
required,  so  that  while  uniform  contact  of  the  surfaces  is  se- 
cured, the  artificial  crown  will  be  made  to  occupy  its  proper 
relative  position  in  the  arch. 

The  articulation  of  the  crown  and  root  may  be  very  accu- 


154  MECHANICAL   DENTISTRY. 

the  rod,  and  thus  indicate  with  certainty  the  depth  of  the  canal. 
The  pivot  being  cut  oif  at  a  point  distant  from  the  crown  equal 
to  the  length  of  the  uncovered  end  of  the  wire,  is  then  dressed 
to  the  size  of  the  orifice  in  the  root.  The  pivot  should  be 
accurately  fitted  to  the  canal  in  the  root,  but  not  so  tightly  as 
to  require  any  greater  force  in  adjusting  the  crown  to  the  root 
than  may  be  readily  applied  with  the  fingers.  A  pivot  thus 
easily  applied  will,  when  enlarged  by  the  absorption  of  fluids, 
be  so  firmly  retained  as  to  render  its  removal  difficult ;  and 
even  when  moisture  is  excluded,  adequate  stability  will  be 
imparted  to  the  attachment,  provided  sufficient  depth  is  given 
to  the  cavity  in  the  root. 

It  may  be  observed,  however,  that  any  method  of  pivoting 
which  does  not  effectually  exclude  the  secretions  of  the  mouth 
is  objectionable.  The  too  frequent  method  of  fixing  artificial 
crowns  with  pivots  of  wood,  without  providing  for  the  exclu- 
sion of  the  oral  secretions  and  pulpy  portions  of  food,  not  only 
hastens  the  destruction  of  the  root,  but,  in  addition  to  being 
positively  harmful,  cannot  fail  to  bring  a  desirable  method  of 
replacement  into  general  and  merited  disrepute  by  reason  of 
the  offensive  odors  accompanying  the  animal  decomposition  in- 
separably associated  with  such  a  mode  of  procedure. 

To  provide  against  the  intrusion  of  the  secretions  or  portions 
of  alimentary  substances,  either  of  the  following  expedients 
may  be  adopted : 

If  the  coaptation  of  the  prepared  surfaces  of  crown  and 
root  in  contact  is  accurate  and  uniform,  one  or  two  thicknesses 
of  No.  4  or  6  gold  foil,  or  corresponding  thickness  of  tin  foil, 
interposed  when  the  crown  is  forced  to  its  place,  will  exclude 
the  secretions  with  tolerable  certainty. 

Such  plastic  substances,  however,  as  are  impervious  and  in- 
soluble will  more  certainly  accomplish  the  object  in  view,  and 
among  these.  Hill's  stopping  is  generally  esteemed  the  best. 

Amalgam  may  also  be  used  for  the  same  purpose,  in  which 
case  the  central  portion  of  the  articulating  surface  of  the  root 
should  be  somewhat  countersunk. 

It  not  unfrequently  happens  that  a  cone  or  funnel-shaped 


PIVOTING    ARTIFICIAL   CROWNS.  155 

enlargement  exists  at  the  orifice  of  the  root-canal  as  the  result 
of  decay.  In  such  cases  it  will  be  difficult  and  often  imprac- 
ticable to  adjust  a  pivot  crown  securely  without  preliminary 
treatment  of  the  root. 

Firmness  of  attachment,  in  these  cases,  may  be  secured  in 
either  of  the  following  ways:  1.  Having  removed  all  softened 
or  decayed  material  from  around  the  orifice  of  the  canal  and 
enlarged  the  latter  to  the  required  depth  for  a  pivot  of  ordi- 
nary length,  the  canal  so  prepared,  together  with  the  carious 
excavation,  may  be  filled  compactly  with  gold  flush  with  the 
margins  of  the  dressed  end  of  the  root.  Through  this  a  cen- 
tral passage  is  made  with  suitable  drills  for  the  admission  of  a 
pivot.  2.  A  highly  polished  and  uniformly  cylindrical  steel 
wire,  somewhat  smaller  than  the  prepared  opening  in  the  root, 
may  be  introduced  into  the  latter  and  gold  packed  around  it 
and  into  the  excavation,  flush,  as  in  the  former  case,  with  the 
margins  of  the  root,  after  which  the  steel  wire  is  carefully 
withdrawn.  In  either  of  the  above  cases  the  gold  should  be 
securely  fixed  in  place  in  the  first  instance  by  forming  small 
pits  or  circular  grooves  in  the  walls  of  the  enlarged  canal,  and 
by  retaining-points  in  the  sides  of  the  excavation. 

Pivots  of  Metal  and  Wood. — Pivots  are  sometimes  formed 
of  gold  wire  encased  in  wood.  These  impart  additional  strength 
to  the  attachment,  and,  at  the  same  time,  enable  the  operator 
to  change  the  direction  of  the  crown  by  bending  the  pivot 
whenever  the  root  stands  irregularly  in  the  arch.  A  hole, 
somewhat  smaller  than  that  in  the  root,  is  drilled  into  a  block 
of  pivot  wood,  and  into  this  is  forced  a  gold  wire — that  formed 
of  gold  and  platinum  being  the  best,  as  it  possesses  greater 
stiifness  and  elasticity.  The  wood  is  then  dressed  down  to  a 
size  a  little  larger  than  the  canal  in  the  root,  and  then  coni- 
jM-essed.  One  end  being  fitted  to  the  hole  in  the  crown,  the 
projecting  portion  of  the  pivot,  cut  to  the  proper  length,  is 
trimmed  to  fit  tlie  opening  in  the  root,  and  applied  in  the  man- 
ner before  described. 

Another  method  is  to  close  the  hole  in  the  crown  with  a 
cylinder  of  j)ivot  wood,  trim  it  even  with  the  base  of  the  crown, 


152  MECHANICAL  DENTISTRY. 

rately  obtained  in  the  following  manner :  Attach  to  the  crown 
a  temporary  pivot  of  wood  that  may  be  easily  applied  and 
removed ;  coat  the  surface  of  the  root  uniformly  with  some 
pigment,  as  carmine,  rouge,  or  rose  pink,  and  apply  the  crown, 
with  pivot  attached,  to  the  root ;  the  points  of  contact  will  be 
indicated  upon  the  base  of  the  crown  by  the  adherent  coloring 
matter ;  the  colored  portions  are  then  ground  down  somewhat 
on  an  emery  wheel,  and  this  process  is  repeated  until  the  entire 
surface  of  the  base  of  the  crown  exposed  to  the  pigment  becomes 
uniformly  coated.  Whenever  it  is  thought  important  to  pre- 
serve the  form  of  the  porcelain  crown  unchanged,  the  operation 
may  be  reversed  by  coloring  the  base  of  the  latter  and  filing 
from  the  extremity  of  the  root  until  a  perfect  adjustment  of 
the  parts  is  secured. 

Another  method,  sometimes  employed,  may  be  adopted,  and 
will  secure  an  equally  accurate  bearing  of  the  crown  without 
subjecting  the  patient  to  the  annoyance  of  repeated  trials  of 
the  pivot  tooth  in  the  mouth.  After  having  prepared  the  root 
in  the  manner  already  described,  an  impression  of  the  root  and 
contiguous  teeth  is  taken,  and  from  this  a  plaster  model  is  ob- 
tained. The  drilled  cavity  in  the  root  will  be  indicated  on  the 
model  by  a  corresponding  depression ;  this  may  be  extended 
into  the  body  of  the  latter  with  an  instrument  fitting  the  ori- 
fice and  held  in  the  exact  position  as  when  enlarging  the  canal 
in  the  fang.  The  model  is  then  varnished,  and  a  pivot  being 
temporarily  attached  to  the  crown,  the  base  of  the  latter  may 
be  ground,  with  or  without  the  use  of  coloring  matter  applied 
to  the  model,  until  the  articulating  surfaces  close  uniformly, 
and  the  crown  occupies  the  required  position  indicated  by  the 
adjoining  teeth  represented  on  the  model.  If  the  impression 
is  correct,  and  the  manipulations  are  accurately  conducted,  a 
pivot  tooth  prepared  in  this  manner  will  be  found  to  fit  the 
root  and  occupy  a  proper  position  in  the  circle  with  but  little, 
if  any,  additional  filing  or  grinding. 

Attaching  the  Oroivn  by  Means  of  Wood  Pivots. — The  older 
and  less  expensive  method  of  fixing  artificial  crowns  to  the 
roots  of  teeth  is  by  means  of  pivots  of  wood.     Thoroughly 


PIVOTING   ARTIFICIAL   CROAVNS.  153 

seasoned  white  hickory  of  small  growth,  fine-grained,  and 
straight,  compact  fibres,  is  esteemed  the  best  for  the  purpose. 
This  substance  is  often  used  in  its  natural  condition,  but  it  will 
be  much  improved,  both  in  respect  to  strength  and  durability, 
if  previously  well  condensed  by  forcing  it  through  the  hol(!S  of 
an  ordinary  draw-plate,  or,  what  is  better,  through  aj)ertures 
of  various  sizes  formed  with  smooth  bevelled  edges  in  a  piece 
of  ivory,  steel,  or  porcelain  of  sufficient  thickness.  Cylinders 
of  wood,  of  uniform  thickness  throughout,  are  most  conve- 
niently formed  by  splitting  the  timber  into  rods  five  or  six 
inches  in  length,  and  from  one-eighth  to  a  quarter  of  an  inch 
in  diameter,  trimming  them  with  suitable  instruments  to  a  size 
one-third  larger  than  required  when  condensed,  and  then  pass- 
ing them  through  the  holes  of  a  draw-plate,  on  the  side  where 
they  form  a  cutting  edge,  commencing  with  the  larger  and 
passing  to  those  of  diminished  calibre,  until  a  cylinder  of  the 


Fio.  45. 


size  mentioned  is  obtained.  These  are  then  compressed  in  the 
manner  V)efore  mentioned.  When  the  draw-i)late  is  used  to 
compress  the  pivot,  the  latter  should  be  passed  through  from 
the  side  opposite  to  the  one  used  in  forming  the  pivot. 

One  end  of  the  pivot,  dressed  to  the  proper  size,  is  maxle  to 
fit  accurately  the  hole  in  the  crown,  care  being  taken  not  to 
fracture  the  latter  when  forcing  the  pivot  into  place.  The 
depth  of  the  enlarged  opening  in  the  root  will  determine  the 
length  to  be  given  to  the  end  of  the  pivot  ]»rojecting  from  the 
crown,  and  the  former  may  be  readily  determined  Ijy  means  of 
a  gauge  (Fig.  45),  cf)nsisting  of  a  rod  of  wire  of  a  size  to  enter 
freely  the  canal  in  the  root,  with  a  movable  slide,  to  the  end  of 
which  is  attached  a  circular  collar  or  flange.  The  end  of"  tiie 
wire  being  pressed  to  the  bottom  of  the  canal,  the  flange,  rest- 
ing against  the  end  of  the  root,  will  force  the  slide  l>a<'k  upon 


154  MECHANICAL   DENTISTEY. 

the  rod,  and  thus  ijidicate  with  certainty  the  depth  of  the  canal. 
The  pivot  being  cut  off  at  a  point  distant  from  the  crown  equal 
to  the  length  of  the  uncovered  end  of  the  wire,  is  then  dressed 
to  the  size  of  the  orifice  in  the  root.  The  pivot  should  be 
accurately  fitted  to  the  canal  in  the  root,  but  not  so  tightly  as 
to  require  any  greater  force  in  adjusting  the  crown  to  the  root 
than  may  be  readily  applied  with  the  fingers.  A  pivot  thus 
easily  applied  will,  when  enlarged  by  the  absorption  of  fluids, 
be  so  firmly  retained  as  to  render  its  removal  difficult ;  and 
even  when  moisture  is  excluded,  adequate  stability  will  be 
imparted  to  the  attachment,  provided  sufficient  depth  is  given 
to  the  cavity  in  the  root. 

It  may  be  observed,  however,  that  any  method  of  pivoting 
which  does  not  effectually  exclude  the  secretions  of  the  mouth 
is  objectionable.  The  too  frequent  method  of  fixing  artificial 
crowns  Avith  pivots  of  wood,  without  providing  for  the  exclu- 
sion of  the  oral  secretions  and  pulpy  portions  of  food,  not  only 
hastens  the  destruction  of  the  root,  but,  in  addition  to  being 
positively  harmful,  cannot  fail  to  bring  a  desirable  method  of 
replacement  into  general  and  merited  disrepute  by  reason  of 
the  offensive  odors  accompanying  the  animal  decomposition  in- 
separably associated  with  such  a  mode  of  procedure. 

To  provide  against  the  intrusion  of  the  secretions  or  portions 
of  alimentary  substances,  either  of  the  following  expedients 
may  be  adopted : 

If  the  coaptation  of  the  prepared  surfaces  of  crown  and 
root  in  contact  is  accurate  and  uniform,  one  or  two  thicknesses 
of  No.  4  or  6  gold  foil,  or  corresponding  thickness  of  tin  foil, 
interposed  when  the  crown  is  forced  to  its  place,  will  exclude 
the  secretions  with  tolerable  certainty. 

Such  plastic  substances,  however,  as  are  impervious  and  in- 
soluble will  more  certainly  accomplish  the  object  in  view,  and 
among  these,  Hill's  stopping  is  generally  esteemed  the  best. 

Amalgam  may  also  be  used  for  the  same  purpose,  in  which 
case  the  central  portion  of  the  articulating  surface  of  the  root 
should  be  somewhat  countersunk. 

It  not  unfrequently  happens  that  a  cone  or  funnel-shaped 


PIVOTIXG    ARTIFICIAL    CROWNS.  155 

enlargement  exists  at  the  orifice  of  the  root-canal  as  the  result 
of  decay.  In  such  cases  it  will  be  difficult  and  often  imprac- 
ticable to  adjust  a  pivot  crown  securely  without  preliminary 
treatment  of  the  root. 

Firmness  of  attachment,  in  these  cases,  may  be  secured  in 
either  of  the  following  ways  :  1.  Having  removed  all  softened 
or  decayed  material  from  around  the  orifice  of  the  canal  and 
enlarged  the  latter  to  the  required  depth  for  a  ])ivot  of  ordi- 
nary length,  the  canal  so  prepared,  together  with  the  carious 
excavation,  may  be  filled  compactly  with  gold  flush  with  the 
margins  of  the  dressed  end  of  the  root.  Through  this  a  cen- 
tral passage  is  made  with  suitable  drills  for  the  admission  of  a 
pivot.  2.  A  highly  polished  and  uniformly  cylindrical  steel 
wire,  somewhat  smaller  than  the  prepared  opening  in  the  root, 
may  be  introduced  into  the  latter  and  gold  packed  around  it 
and  into  the  excavation,  flush,  as  in  the  former  case,  with  the 
margins  of  the  root,  after  which  the  steel  wire  is  carefully 
withdrawn.  In  either  of  the  above  cases  the  gold  should  be 
securely  fixed  in  place  in  the  first  instance  by  forming  small 
pits  or  circular  grooves  in  the  walls  of  the  enlarged  canal,  and 
by  retaining-points  in  the  sides  of  the  excavation. 

Pivots  of  Metal  and  Wood. — Pivots  are  sometimes  formed 
of  gold  wire  encased  in  wood.  These  impart  additional  strength 
to  the  attachment,  and,  at  the  same  time,  enable  the  operator 
to  change  the  direction  of  the  crown  by  bending  the  pivot 
whenever  the  root  stands  irregularly  in  the  arch.  A  hole, 
somewhat  smaller  than  that  in  the  root,  is  drilled  into  a  block 
of  pivot  wood,  and  into  this  is  forced  a  gold  wire — that  formed 
of  gold  and  platinum  being  the  best,  as  it  possesses  greater 
stiffness  and  elasticity.  The  wood  is  then  dressed  down  to  a 
size  a  little  larger  than  the  canal  in  the  root,  and  then  com- 
pressed. One  end  being  fitted  to  the  hole  in  the  crown,  the 
projecting  portion  of  the  pivot,  cut  to  the  jtroper  length,  is 
trimme<l  to  fit  the  opening  in  the  root,  and  applied  in  the  man- 
ner before  dc^scribed. 

Anotlier  method  is  to  close  the  hole  in  the  crown  with  a 
cylinder  of  pivot  wood,  trim  it  even  with  the  base  of  the  crown, 


156  MECHANICAL   DENTISTRY. 

perforate  its  centre  with  a  drill^  and  introduce  into  this  one 
end  of  the  wire,  the  surface  of  which  is  cut  up  into  small  barbs, 
or  otherwise  roughened  to  prevent  it  from  drawing.  A  similar 
piece  of  wood  is  fitted  to  the  orifice  in  the  fang,  and  trimmed 
and  drilled  in  like  manner  for  the  reception  of  the  wire  pivot 
— the  latter  being  barbed  and  filed  square  to  render  it  station- 
ary when  forced  into  place. 

The  author,  in  a  number  of  cases,  has  adopted  the  following 
methods  of  inserting  pivot  teeth,  in  connection  with  the  use  of 
rubber,  with  gratifying  results. 

Having  prepared  the  root  in  the  ordinary  manner,  select 
and  fit  the  pivot  crown  to  the  vacuity,  leaving  something  of  a 
space  posteriorly  between  the  base  of  the  crown  and  the  root. 
Fit  a  temporary  wood  pivot  to  the  enlarged  opening  in  the 
root,  accurately,  but  in  such  manner  that  it  may  be  easily  with- 
drawn ;  the  end  projecting  from  the  root  should  be  trimmed 
down  to  say  half  the  diameter  of  the  hole  in  the  crown,  so  that 
when  the  latter  is  applied  in  the  manner  to  be  mentioned 
directly,  some  latitude  of  movement  will  be  provided,  admit- 
ting of  a  proper  adjustment  of  the  crown  when  applied  to  the 
space.  With  the  wood  pivot  in  the  root,  fill  the  hole  in  the 
crown  with  stiffened  wax,  warm  the  pivot  crown  sufficiently  to 
soften  the  wax,  and  apply  it  to  the  root  in  the  desired  position 
with  respect  to  the  other  teeth.  When  the  wax  has  hardened 
somewhat,  withdraw  the  crown  carefully  on  a  line  with  the 
pivot,  bringing  the  latter  with  it;  then  add  sufficient  softened 
wax  to  the  base  of  the  crown  to  fill  in  the  gap  or  space  between 
the  croM^n  and  root ;  replace  the  tooth  with  the  pivot  attached, 
and  press  up  until  the  crown  again  takes  its  proper  position 
in  the  vacuity.  By  this  means  we  get  an  impression  of  the 
filed  extremity  of  the  root,  and,  at  the  same  time,  secure  an 
accurate  relation  of  all  the  parts.  The  crown  and  pivot  are 
then  carefully  removed.  Now  take  plaster  and  pour  a  small 
quantity  on  a  piece  of  paper  or  card  and  sink  the  pivot  into  it 
until  the  surface  of  the  wax  at  the  base  of  the  crown  rests 
upon  the  plaster,  and  then  build  the  latter  up  upon  the  front 
part  of  the  crown  to  the  cutting  edge,  thus  forming  a  shallow 


PIVOTING   ARTIFICIAL   CROWNS.  157 

bed  for  its  anterior  face.  When  the  plaster  has  hardened, 
warm  the  model  to  soften  the  wax,  and  then  remove  the  crown 
and  wax ;  the  pivot  will  be  found  remaining  in  the  model,  but 
which,  if  previously  oiled,  can  be  readily  drawn.  We  have 
now  in  the  model  an  accurate  representation  of  the  end  of  the 
root,  the  size  and  direction  of  the  root-canal,  and,  when  the 
crown  is  replaced  in  its  shallow  bed,  also  the  space  between 
the  crown  and  root  to  be  filled  in  with  rubber.  The  hole  in 
the  model,  corresponding  with  that  in  the  root,  should  be  en- 
larged somewhat,  and  this  may  be  done  with  the  same  drill 
used  in  enlarging  the  orifice  of  the  root.  After  varnishing  the 
hole  in  the  model,  pack  in  softened  rubber  until  full,  and  in- 
sert into  this  the  gold  wire  previously  heated,  the  crown  end 
of  the  wire  projecting  a  line  or  so.  Next  fill  the  hole  in  the 
crow^n  with  rubber,  heat  the  crown,  and  press  it  down  upon 
the  model  and  over  the  gold  wire  until  the  crown  goes  accu- 
rately into  the  depression  made  for  it  in  the  model.  Then  pack 
softened  rubber  into  the  space  between  the  base  of  the  crown 
and  the  model  until  it  is  filled  in  compactly.  The  whole  is 
then  encased  in  plaster,  confined  in  a  flask,  and  vulcanized. 
If  the  foregoing  manipulations  are  carefully  conducted,  the 
crown  will  go  to  its  place  in  the  mouth  with  unerring  accuracy, 
and,  by  placing  one  or  two  thicknesses  of  gold  foil  between 
the  rubber  and  root,  or  some  plastic  material,  as  Hill's  stop- 
ping, the  joint  will  be  rendered  impervious.  There  is  still  an 
additional  advantage  in  this  method.  All  are  aware  of  the 
liability  of  a  wood  pivot  drawing  from  the  crown  where  the 
latter  is  short  and  tiie  hole  in  it  shallow.  The  wired  rubber 
pivot,  vulcanized  in  the  crown,  cannot  be  drawn  from  the 
most  shallow  cavity  without  fracturing  the  crown.  In  very 
many  cases  this  circumstance  is  of  great  value. 

In  sul>stituting  a  porcelain  plate  tooth  for  the  pivot  crown 
in  connection  with  the  use  of  rubber  the  following  method  may 
be  j)ursued  :  Fit  a  metallic  pivot,  composed  of  gold  and  pla- 
tinum, accurately  to  the  enlarged  opening  in  the  root,  but  not 
HO  tiglitly  but  that  it  may  be  readily  withdrawn.  Select  and 
fit  a  suitable  plate  tooth,  and  solder  to  this  a  moderately  thin 


158  MECHANICAL    DENTISTRY. 

gold  backing.  If,  on  reapplying  the  crown,  with  the  pivot  in 
place,  the  former  is  crowded  forward  out  of  proper  position  by 
the  pivot,  cut  a  slot  in  the  latter,  and,  if  necessary,  groove  the 
gold  backing  and  crown  at  the  base  of  the  latter  until  the 
crown  will  take  its  required  place,  and  the  projecting  portion 
of  the.  pivot  lies  in  close  contact  with  the  gold  backing  for  a 
distance  sufficient  to  insure  adequate  strength  of  attachment 
when  the  two  are  united  by  solder.  When  the  crown  is  thus 
adjusted  to  the  pivot,  secure  them  in  this  relation  with  wax  or 
plaster  and  remove  them  carefully ;  imbed  in  plaster  and  unite 
them  securely  with  solder,  and  then  proceed  to  take  an  accurate 
impression  of  the  end  of  the  root  in  connection  with  the  united 
crown  and  pivot.  This  may  be  done  by  first  filling  in  over 
the  dressed  end  of  the  root  with  a  sufficient  quantity  of  soft- 
ened wax,  forcing  the  crown  and  pivot  into  place,  and  then 
moulding  the  wax  with  the  finger  to  the  end  of  the  root  and 
over  the  backing.  Trim  away  superfluous  portions  of  wax, 
remove  carefully,  imbed  in  plaster  in  the  same  manner  as  de- 
scribed in  connection  with  pivot  crown,  form  matrix  in  plaster, 
pack  with  rubber,  vulcanize,  dress  down  to  the  form  of  adjoin- 
ing crowns,  and  polish. 

To  secure  more  perfectly  the  attachment  of  the  rubber,  the 
porcelain  crown  may  be  sufficiently  undercut  with  a  corundum 
disk  along  the  sides  of  the  gold  backing,  to  bind  the  rubber, 
and  this  should  be  done  either  before  or  immediately  after 
soldering  the  pivot  to  the  crown. 

AVhen  employing  either  of  the  foregoing  methods,  the  wire 
pivot  should  be  well  barbed,  and  the  joint  between  the  crown 
and  root  sealed  either  by  interposing  folds  of  soft  foil,  or  by 
some  durable  and  impervious  plastic  material  when  the  crown 
is  finally  and  permanently  adjusted. 

Pivot  Plate. — The  following  methods  of  pivoting  an  arti- 
ficial crown  are  applicable  to  all  cases  admitting  of  this  mode 
of  substitution,  but  will  be  found  of  especial  utility  under 
certain  circumstances  or  conditions  which  exclude  the  use  of 
the  simple  pivot  crown,  or  which  at  least  render  their  employ- 
ment difficult  and  unsatisfactorv. 


PIVOTING   ARTIFICIAL    CROAVNS.  159 

It  frequently  occurs  that  the  root  to  be  used  occupies  a  posi- 
tion in  the  arch  inconsistent  with  a  harmonious  arrangement  of 
the  tooth  of  replacement  by  the  usual  method  of  attaching  an 
ordinary  pivot-crown.  Thus  it  may  lie  closely  against  one  or 
other  of  the  adjoining  teeth,  distant  from  the  centre  of  the 
space ;  or  it  may  have  too  great  an  anterior  or  posterior  ob- 
liquity, or  too  great  a  lateral  inclination;  or,  again,  it  may 
range  with  the  other  teeth  with  respect  to  its  direction,  but  may 
occupy  a  position  entirely  within  the  circle ;  in  either  case  it 
will  be  difficult  or  impracticable  to  give  a  proper  relative  posi- 
tion to  the  crown  in  the  usual  way.  It  is  true  that  any  slight 
deviation  from  a  just  position  or  inclination  of  the  root  may 
be  compensated  for  by  a  corresponding  inflection  of  the  pivot, 
or  by  forming  an  abrupt  angle  to  it  where  the  crown  and  root 
unite,  or  by  placing  the  pivot  on  one  side  of  the  hole  in  the 
crown  ;  but  when  the  irregularities  spoken  of  exist  to  any  con- 
siderable extent,  it  will  become  necessary  to  adjust  a  pivot-plate 
to  the  root,  and  attach  to  the  base  an  ordinary  plate  tooth,  to 
which  any  desired  position  may  be  assigned. 

One  of  the  simplest  and  most  practicable  methods  of  per- 
forming this  operation  is  thus  described  by  Professor  Edwin 
T.  Darby: 

"  After  this  (the  proper  preparation  of  the  root)  has  been 
thoroughly  done,  select  a  piece  of  gold  or  platinum  wire  («), 
Fig.  40,  of  the  diameter  of  the  opening  in  root,  and  fit  nicely 


Fig.  4G 

I    © 


tt 


to  the  opening,  letting  it  project  one-eighth  inch  beyond  the 
end  of  the  root,  that  it  may  be  readily  removed  and  inserted 
in  the  root  during  the  operation.  Next  select  a  thin  piece  of 
platinum,  of  which  make  a  cap  with  hole  to  fit  around  the 
wire   pivot  snugly,  and  over  the  whole  end  of  the  root  (6). 


162 


MECHANICAL   DENTISTEY. 


is  here  given  (Fig.  47,  o).  When  this  is  done  and  the  wire 
and  plate  taken  from  the  root  and  put  in  place  in  the  impres- 
sion, a  correct  model  of  the  teeth  and  parts  adjoining  can  be 
made  with  the  gold  in  the  same  relative  position  as  when  in 
the  mouth.  After  the  model  is  made,  the  gold  removed  from 
it,  the  end  of  the  wire  which  extended  outside  the  root  to  aid 
in  marking  the  position  of  the  wire  and  plate  in  the  impres- 
sion cut  off  and  filed  down  to  the  surface  of  the  plate,  a  thick, 
narrow  gold  backing  should  be  fitted  and  riveted  to  a  suitable 
crown  (plain  'plate  tooth'  with  'straight  pins')  and  a  groove 
be  cut  along  each  side,  and,  in  some  cases,  near  the  cutting 
edge  of  the  porcelain,  as  illustrated  in  Figs.  47  6,  and  48. 
This  is  done  that  the  parts  may  then  be  built  out  and  the  por- 
celain more  perfectly  secured,  and  the  contour  of  the  palatal 


Fig.  47. 


Fig.  48. 


portion  restored  with  pure  gold,  as  shown  in  the  cut  with 
crown  in  place  (Fig.  48).  After  the  backing  is  placed  upon 
the  porcelain,  it  should  be  attached  to  the  plate  with  wax  and 
the  whole  carefully  removed  from  the  model,  encased  in  plas- 
ter and  sand,  gradually  heated,  and  soldered.  The  parts,  pre- 
pared as  described  and  illustrated,  may  be  held  by  screwing 
the  wire  in  a  hand-vice  while  the  gold  foil  is  being  built  in 
place.  This  can  be  nicely  done  with  the  electro-magnetic 
mallet,  and  the  crown  made  ready  for  insertion  by  the  time  of 
the  next  appointment  with  the  patient. 

"  A  very  good  and  less  difficult  method  of  preparing  crowns 
is  to  back  the  whole  of  the  porcelain  and  restore  the  contour 
of  the  palatal  portion  with  fine  gold  plate  (18  to  22  k.), 
united  with  correspondingly  fine  solder. 

"  The  apical  foramen  should  be  closed  with  gold.  If  gutta- 
percha or  oxychloride  of  zinc  be  used  for  this  purpose,  some  of 


PIVOTING   ARTIFICIAL   CROWNS.  163 

the  material  may  be  pressed  through  the  foramen,  but  with 
gold  the  operation  can  be  made  more  certain  and  satisfactory. 
To  avoid  any  exposure  of  gold  should  recession  of  the  gum 
take  place,  the  edge  of  the  plate  ought  to  be  so  cut  away  that 
the  porcelain  may  be  accurately  fitted  upon  the  labial  portion 
of  the  root. 

"  When  all  is  in  readiness  for  placing  the  crown  upon  the 
root,  fine  barbs  should  be  made  with  a  knife  or  lancet  along 
the  entire  surface  of  the  gold  wire,  a  thin  layer  of  white  gutta- 
percha (such  as  requires  little  heat)  placed  around  the  wires 
and  against  the  plate ;  the  metallic  parts  should  be  heated  suf- 
ficiently to  just  soften  the  gutta-percha,  and,  with  the  root 
dried,  the  whole  must  be  immediately  pressed  and  carefully 
malleted  to  place.  The  surplus  stopping  should  be  trimmed 
oif  with  a  lancet  a  few  hours  or  the  day  after  the  crown  is 
placed  upon  the  root,  or  when  the  gutta-percha  shall  be  thor- 
oughly cooled  ;  the  gum  will  then  have  been  so  pressed  away 
that  the  boundary-line  between  the  crown  and  root  can  be  seen 
and  the  edge  of  the  gutta-percha  smoothly  finished  with  pellets 
of  Japanese  bibulous  paper,  lint,  or  cotton  saturated  with  chlo- 
roform. 

"  There  is  a  still  less  difficult  and  yet  good  method  of  plac- 
ing crowns  upon  roots  of  teeth,  and  one,  too,  that  does  not  re- 
quire so  much  time  as  that  just  described  ;  but  the  root  should 
be  prepared  and  a  gold  wire  fitted  in  it  in  the  same  manner. 
A  suitable  plain  'pivot'  crown,  having  a  hole  in  it  a  little 
larger  than  the  gold  wire,  should  be  selected  and  fitted  to  the 
surface  of  the  root  as  perfectly  as  possible,  and  the  opening  in 
the  porcelain  filled  with  fine,  well-seasoned  hickory  wood, 
which  must  then  be  cut  off  even  with  the  base  of  the  crown, 
and  a  hole  drilled  in  the  centre  and  entirely  through  it  large 
enough  to  insert  one  end  of  the  wire.  The  surface  of  the  wire 
should  l)c  roughened  or  finely  barbed  along  its  whole  length, 
one  end  })]aced  (not  malleted)  tightly  in  the  opening  made  for 
it  in  the  wood  in  the  crown,  and  the  whole  then  placed  upon 
the  root  and  finished  Jis  above  descril)ed. 

"An  artificial  crown,  l)y  whatever  method  mounted,  can  be 


164 


MECHANICAL   DENTISTEY. 


■  more  successfully  placed  upon  a  root,  and  all  operations  better 
performed,  when  the  rubber  dam  is  applied  than  where  it  is 
not  used,  and  it  should,  therefore,  be  secured,  if  the  operator 
can  apply  it,  to  the  adjoiniug  teeth,  and  then  to  the  root,  be- 
fore the  final  fitting  and  mounting  of  the  crown." 

Gold  Crown  Faced  with  Porcelain. — The  subjoined  method 
of  attaching  an  artificial  crown  to  a  root  was  originally  intro- 
duced to  the  notice  of  the  profession,  in  1872,  by  Dr.  Marshall 
H.  Webb.  The  following  is  a  description  of  his  more  recent 
and  perfected  method  of  operating,  which,  while  it  necessitates 
great  care,  dexterity,  and  delicacy  of  manipulation,  unquestion- 
ably possesses,  in  aa  exceptional  degree,  the  important  advan- 
tages not  only  of  security  of  attachment,  but  of  indestructi- 
bility, the  union  with  the  prepared  surface  of  the  root  being 
effected  by  direct  contact  of  impacted  gold. 

"  Building  crowns  of  gold  upon  roots  of  teeth  and  facing 
them  with  porcelain  makes  the  most  secure  and  satisfactory 


though  difficult  operation.  After  preparing  the  root,  closing 
the  foramen  with  gold,  and  cutting  away  the  irregular  or  pro- 
jecting edges  to  within  about  a  half  line  of  the  margin  of  the 
gum  (leaving  this  much  to  aid  in  applying  the  rubber  dam),  a 
gold  wire,  No.  13  or  14,  with  a  fine,  sharp  thread  cut  upon  it, 
should  be  accurately  fitted  in  the  pulp-chamber  to  near  the 
apical  foramen.  To  the  platinum  pins  of  the  porcelain  selected 
for  the  case  a  cylinder  or  tube  made  of  gold  plate  should  be 
fitted,  and,  after  it  is  opened  (Fig.  49),  riveted  and  then  closed, 
placed  in  plaster  and  fine  sand,  and  carefully  heated  and  sol- 
dered.    A  thread  must  then  be  cut  in  the  cylinder  correspond- 


PIVOTIXG   ARTIFICIAL    CROWNS.  165 

ing  to  that  upon  the  wire  to  which  it  is  to  be  attached.  This 
is  done  that  the  crown  may  be  more  securely  placed  upon  the 
root  than  by  the  method  described  by  the  writer  in  the  Dental 
Cosmos,  June,  1873.  The  end  of  the  gold  tube  next  the  cut- 
ting edge  of  the  crown  may  be  bevelled  and  a  slot  made  in  the 
wire  at  that  part,  so  that  the  cylinder  will  be  prevented  from 
turning,  while  still  greater  strength  is  added  by  impacting  gold 
into  the  open  part,  thus  spreading  the  end  of  the  wire.  A 
groove  should  be  cut  with  a  corundum  disk  in  each  side  (6), 
and  sometimes  along  the  cutting  edge  of  the  porcelain,  into 
which  gold  foil  is  to  be  placed,  to  secure  greater  strength  and 
permanency. 

"  When  all  is  in  readiness  for  the  operation,  the  rubber  dam 
should  be  applied  to  two  teeth  each  side  of  the  root  and  to  the 
root  itself.  The  ligature  of  waxed  floss  silk  should  be  placed 
twice  around  the  root,  tightened,  and  pressed  well  to  place  with 
a  burnisher,  the  ends  of  the  silk  wrapped  twice,  as  in  tying  a 
surgeon's  knot,  and  the  ligature  then  attached  to  the  ring  at 
the  end  of  an  elastic  rubber  dam  holder  and  held  just  below 
the  edge  of  the  slightly  upraised  lip,  so  that,  when  the  holder 
is  fixed  to  a  tie  put  around  the  patient's  neck,  there  shall  be 
constant  tension  upon  the  ligature.  After  this  has  been  done 
the  root  should  be  trimmed  down  with  corundum  wheels  or 
cones  to  the  ligature,  although  not  close  enough  to  displace  it. 
The  porcelain  should  then  be  so  fitted  as  to  leave  a  half  line 
of  space  to  be  filled  with  gold  (as  at  c)  between  it  and  the  root, 
after  the  wire  has  been  placed  in  the  cylinder  and  screwed  into 
the  root.  In  placing  the  parts  in  position  a  little  oxychloride 
of  zinc,  nearly  the  consistency  of  cream,  should  be  placed  in 
the  root  next  the  gold  that  closes  the  foramen,  and  the  gold 
wire  at  once  put  in  this  and  screwed  securely  to  place.  After 
the  oxychloride  of  zinc  has  crystallized,  sufficient  of  it  and  of 
the  dentine  should  be  cut  away  with  small  burs  to  secure  good 
anchorage  for  the  gold  now  to  be  placed  as  perfectly  and  solidly 
as  possible  around  the  wire,  to  and  over  the  margin  of  the  root, 
along  the  gold  tube,  into  the  grooves  made  in  the  porcelain, 
and  betwficn  it  and  the  labial  margin  of  the  root  (c).     This 


166  MECHANICAL   DENTISTEY. 

narrow  line  of  gold  need  not  be  made  visible  when  the  oper- 
ation is  completed.  The  gum  should  cover  it.  While  the 
gold  is  being  placed  around  the  wire  in  the  root  the  porcelain 
can  be  turned  a  little  to  one  side  upon  the  gold  wire  till  the 
cylinder  is  reached  and  restoration  of  the  contour  of  the  parts 
commenced.  All  the  gold  should  be  cohesive  and  impacted  by 
the  aid  of  the  electro-magnetic  mallet,  with  which  the  surplus 
foil  can  easily  be  trimmed  away  from  the  margin  of  the  root 
as  placed  upon  it,  and  the  form  of  the  crown  so  nicely  carried 
forward  that  but  little  dressing  is  afterwards  necessary.  The 
gold  should  be  filed  even  with  the  margin  of  the  root,  and 
finished  with  narrow  strips  of  fine  emery  cloth  at  and  near  that 
point,  while  the  rubber  dam  is  yet  in  place;  after  this  is  re- 
moved the  gold  should  be  so  cut  away  as  to  allow  proper  occlu- 
sion of  the  teeth,  and  a  little  space  should  afterwards  be  gained 
by  very  careful  wedging  for  the  trimming  and  finishing  of  the 
gold  along  each  proximate  surface  separately." 

The  form  and  relations  of  the  several  parts  entering  into  the 
construction  of  a  crown  by  Dr.  Webb's  method  are  shown  in 
Fig.  49. 

A  process  of  attaching  porcelain  crowns  to  the  roots  of  teeth 
by  the  use  of  steel  screws,  originally  introduced  to  the  notice 
of  the  profession  by  Dr.  George  T.  Moffat,  of  Boston,  Mass., 
but  more  recently  and  particularly  described  by  Dr.  E.  W. 
Foster  of  the  same  city,  is  worthy  of  a  place  among  the  best 
operations  of  this  kind  by  reason  of  its  simplicity,  security  of 
attachment,  comparative  inexpensiveness,  and  its  practicable 
application  to  other  than  the  single-rooted  teeth.  Dr.  F.  thus 
describes  the  method : 

"  Among  the  principal  features  of  this  method  is  the  steel 
screw  in  place  of  the  steel  pin,  as  first  applied,  and  which 
unites  the  crown  to  the  root  in  the  most  perfect  and  absolute 
manner.  The  inner  head  of  the  screw  (Fig.  50  a)  is  a  concave 
or  half  globular,  and  completes  the  principle  of  a  ball-and- 
socket  joint  between  itself  and  the  circular  cavity  in  the  poste- 
rior part  of  the  crown,  seen  at  b,  in  a  vertical  section  of  the 
same.     This,  it  will  be  observed,  permits  of  an  automatic  ad- 


PIVOTING    ARTIFICIAL    CROWNS.  167 

justment  to  the  root,  but  more  so  in  lateral  directions,  a  fact  of 
great  importance  and  convenience  where  the  root  is  out  of  its 
normal  position,  as  is  frequently  the  case,  especially  as  regards 
the  anterior  teeth.  Where  the  root  is  sound  and  the  joint  close, 
a  few  layers  of  soft  gold  foil  are  placed  between  the  crown  and 
the  root.  After  a  careful  and  final  setting  of  the  screw,  an 
impervious  joint  is  thereby  obtained — one  perfectly  odorless 
and  highly  antiseptic  to  the  root  for  an  indefinite  period  of 
time. 

"  The  prejudice  against  the  old  and  odorous  varieties  of 
crowns  is  well  sustained  by  all  persons  of  intelligence  and  re- 
finement. 

"  The  front  view  of  an  incisor  crown  thus  set  is  shown  at  a 
(Fig.  51).     The  posterior  cavity  in  the  crown,  over  the  screw- 

FiG.  50.  Fig.  51. 


head  at  6,  is  filled  with  gold,  or  other  material,  and  finished 
flush  and  smooth  with  the  surfaee.  Where  gold  is  u.sed,  which 
is  generally  preferable,  the  retention  of  the  first  pellets  is 
greatly  facilitated  by  the  previous  arrangement  of  a  few  layers 
of  adhesive  gold  foil  under  the  head  of  the  screw,  whose  over- 
lapping edges  serve  admirably  the  purpose  intended. 

"  Oxychloride  of  zinc  or  gutta-percha  would  be  indicated  in 
cases  where  the  root  was  hypersensitive.  In  the  place  of  the 
layer  or  layers  of  foil  in  the  joint,  a  drop  of  gum  sandarac 
varnish — quite  thick — will  often  be  all  that  is  required  to  ac- 
complish the  same  results.  Where  the  end  of  the  root  is  ex- 
tensively decayed,  the  jagged  interval  in  adjustment  may  be 
filled  with  gold  or  gutta-percha  according  to  the  judgment  of 
the  operator.     The  screws  should  be  made  of  the  best  watch- 


168  MECHANICAL   DENTISTRY. 

steel  wire,  and  in  the  main  shaft  do  not  require  to  be  larger  in 
diameter  than  a  small  knitting  or  common-sized  darning-needle. 
The  screws  may  be  also  slightly  washed  in  a  nickel  bath  to  suit  a 
whim  or  fancy,  but  practically  they  have  no  advantage  what- 
ever over  plain  screws,  for  the  obvious  reasons  of  their  seclu- 
sion and  dryness  when  in  position.  Most  of  the  anterior  roots 
will,  for  a  sufficient  distance,  permit  the  use  of  a  drill  which 
is  three  or  four,  or  even  five  times  the  diameter  of  the  screw. 
A  plug  of  hickory  in  such  cases  is  firmly  set  in  the  hole  thus 
drilled  in  the  root,  and  the  end  of  the  wood  neatly  finished  with 
the  outer  surface.  The  tooth  crown,  now  firmly  held  in  the 
desired  position  on  the  end  of  the  prepared  root,  will  act  as  a 
guide  in  drilling  for  the  screw,  the  drill  passing  up  through 
the  posterior  cavity  of  the  crown.  Presuming,  of  course,  that 
the  nerve  cavity  is  filled  to  the  screw  with  gold,  a  vertical  half 
section  of  the  root  and  crown  with  the  inserted  wood  for  the 
attachment  of  the  screw  would  appear  as  in  Fig.  52.     At  a 

Fig.  52.  Fig.  53. 


appears  the  wood,  and  at  b  the  external  gold  plug.  The  final 
attachment  is  facilitated  by  having  previously  run  the  screw 
once  through  the  wood  before  the  crown  is  put  on.  A  tap  for 
the  screw  is  easily  made  from  a  broken  excavator  or  other  in- 
strument of  like  dimensions  by  drawing  the  temper  and  cutting 
the  same  thread  as  the  screw  for  a  suitable  distance  upon  the 
end.  After  the  end  is  slightly  rounded,  three  grooves,  equi- 
distant from  each  other,  should  be  filed  rather  deeply,  length- 
wise of  the  tap,  then  the  whole  tempered  and  drawn  back  to 
straw  color.  The  screws  themselves  will  run  better  by  being 
grooved  likewise,  but  should  not  be  tempered.     However,  if  a 


PIVOTING   ARTIFICIAL    CROWNS.  169 

tap  is  necessary,  and  a  regular  one  is  not  at  hand,  from  acci- 
dent or  otherwise,  the  screw,  already  grooved,  needs  simply  to 
be  tempered  to  act  admirably  in  a  double  capacity. 

"We  have  spoken  principally  of  the  anterior  teeth.  We 
will  now  refer  to  this  method  as  applied  to  those  teeth,  in  either 
arch,  that  are  posterior  to  the  canines. 

"  It  will  be  evident  from  the  principles  involved,  that  bicus- 
pid and  molar  crowns  can  be  applied  with  the  same  facility, 
especially  whenever  their  situation  in  the  arch  will  permit  the 
use  of  the  drill.  Bicuspids  are  treated  in  the  same  manner  as 
the  anterior  teeth,  save  that  in  the  strong,  broad,  and  frequently 
bifid  roots  of  second  bicuspids,  two  screws  may  attach  the 
crown,  especially  where  extra  strength  will  be  required  from 
their  situation  in  mastication. 

"Fig.  53  will  illustrate  a  second  upper  bicuspid,  in  part  sec- 
tion vv-ith  two  screW'S.  Upper  and  lower  molars  will  require 
two,  three,  or  more  screws  as  the  operator  may  determine, 
]Many  more  layers  of  foil  will  be  required  for  molar  crowns  than 
for  others,  in  order  to  secure  an  equal  perfection  of  their  joints. 
Where  many  crowns  may  be  called  for  in  a  case,  the  carver  is 
indispensable.  In  cities,  and  in  offices,  even,  where  good 
carvers  may  be  had,  nearly,  if  not  every  tooth  may  be  carved 
by  him  to  suit  each  place  precisely,  and  little  or  no  fitting  will 
be  required.  More  diversified  and  desirable  results  are  thus 
obtained.  In  the  country,  and  places  too  remote  for  such  ad- 
vantages, the  anterior  and  bicuspid  crowns  may  be  furnished 
in  various  colors  and  shapes  after  the  ordinary  patterns.  Excel- 
lent crowns  of  the  above  description  have  been  furnished  us  by 
the  enterprise  and  accommodation  of  S.  S.  White  from  moulds 
made  expressly  for  such. 

"  In  the  matter  of  screws  we  will  merely  remark  that,  as  no 
town  furnishes  a  dentist  without  at  the  same  time  furnishing 
him  with  a  neighbor  equally  constant,  omnipresent,  and  inde- 
fatigable,— the  jeweller, — the  facility  of  obtaining  screws  made 
to  a  desirable  j)attorn  will  be  abundant  and  satisfactory. 
Where  it  is  decided  to  give  the  carver  an  opportunity  to  dis- 
play his  skill,  whether  it  be  upon  one  crown  or  a  dozen,  an 


170  MECHANICAL   DENTISTEY. 

impression  in  plaster  will  be  necessary.  Preceding  this,  all  the 
crown-bearing  roots  should  be  prepared,  dressed,  and  drilled 
the  same  as  for  setting,  but  not  tapped.  Bits  of  wire  of  any- 
kind,  the  diameter  of  the  drill,  are  now  set  in  each  place  in- 
tended for  a  screw,  and  rising  to  the  height  of  the  future  crown. 
These  pins  should  sit  in  their  places  easily  enough  to  come 
away  readily  with  the  impression  when  it  is  withdrawn.  The 
removal  of  the  impression  from  about  the  other  teeth  may  be 
facilitated  by  the  use  of  a  slight  portion  of  glycerin  applied 
with  a  small  camel's-hair  brush  about  their  necks  and  crowns. 
Glycerin,  though  agreeable  of  itself  to  most  people,  may  be 
rendered  quite  so  by  perfuming  it  with  some  generally  accept- 
able odor.  The  impression  being  now  removed  is  carefully 
varnished  and  oiled,  the  pin  or  pins  remaining  in  situ.  From 
this  the  true  cast  is  made,  the  pins  now  being  transferred  to 
this  one  in  turn.  By  careful  manipulation  and  cutting  the 
pins  will  part  with  the  old  cast  or  impression  with  little  or  no 
difficulty.  The  purpose  of  these  pins  is  to  serve  the  carver 
for  attachment  of  the  '  body '  in  its  first  moulding,  and  give, 
at  the  same  time,  the  direction  and  diameter  of  the  screws  in 
the  crown,  the  heads  of  which  should  finally  occupy  the  posi- 
tion of  about  a  sixteenth  of  an  inch  from  the  joint.  A  plaster 
bite  of  the  antagonizing  teeth  should  also  accompany  the  final 
cast.  If  shrinkage  in  baking  of  the  crown  will  not  permit 
the  passage  of  the  screw  freely,  a  small,  soft  steel  mandril  in 
the  lathe,  with  the  use  of  oil  and  the  flour  of  emery,  will  be 
efficient. 

"  Fig.  54  represents  a  case  where  eight  crowns  have  been  set 
by  this  method.  The  black  dots  represent  the  gold  fillings 
over  the  screws — two  in  the  second  bicuspid  and  three  in  each 
of  the  two  molars. 

"  In  conclusion,  with  regard  to  the  above  method  of  crowning 
roots,  and  its  application,  we  may  be  permitted  to  offer  for 
consideration  a  summary  of  its  characteristics ; 

"  1st.  Its  simplicity,  neatness,  and  permanency. 

"  2d.  The  impervious  and  antiseptic  character  of  the  union  of 
crown  and  root. 


PIVOTING   ARTIFICIAL    CROWNS. 


171 


"  3d.  The  practical  application  of  these  crowns  to  bicuspids 
and  molars,  as  well  as  to  the  anterior  teeth,  which  have  been 
chiefly  concerned  in  this  matter  hitherto. 

"4th.  The  use  of  the  screw,  which  is  one  of  the  most  pow- 
erful adjuncts  in  mechanics;  and  this  screw  of  steel,  uniting 
the  minimum  of  size  with  the  maximum  of  strength. 

"  5th.  The  application  of  an  entire  crown  of  porcelain,  ivory, 
or  gold  and  porcelain,  as  set  forth. 

Fig.  54. 


"6th.  The  ball-and-socket  principle  of  the  screw-head  and 
its  cavity  of  reception  in  the  crown,  permitting  of  automatic 
adjustment  to  the  root,  whether  in  its  normal  position  or  other- 
wise. 

"  7th.  The  facility  with  which  the  carver  may  adapt  one  or 
many  crowns  in  cither  dental  arch. 

"  8th.  The  final  filling  and  finish  of  gold  or  other  material 
in  the  posterior  cavity  over  the  screw,  sealing  the  whole  imper- 
viou.sly,  and  at  the  same  time  permitting  of  the  speedy  and  safe 
removal  of  the  crown,  when  necessary  from  its  fracture,  or 
from  other  causes. 

"  *Jth.  The  many  objections  it  refutes  witii   regard  to  the 


172  MECHANICAL   DENTISTEY. 

popular  notion  of  'pivoting'  teeth  in  general.  Among  the 
raost  j)rominent  of  which  are  not  only  the  oifensive  odor  and 
other  imperfections  of  the  older  forms,  but  the  costliness  and 
tediousness  of  some  of  the  later  ones." 

The  author  is  indebted  to  the  obliging  courtesy  of  Dr.  W. 
G.  A.  Bonwill,  of  Philadelphia,  Pennsylvania,  for  advance 
proof-sheets  of  an  article  descriptive  of  a  "  New  Method  of 
Substituting  an  All-poecelain  Crown  upon  any  Koot 
IN  Either  Denture/'  prepared  for  August  number  (1880) 
of  the  Dental  Cosmos.  Dr.  Bonwill's  long-continued,  intelli- 
gent, and  successful  experimentation  in  this  sj)ecial  department 
of  practice  is  well  known  to  the  profession,  and  the  following 
may  be  accepted  as  embodying  his  best  and  latest  experiences. 
He  writes : 

"No  argument  is  needed  to  convince  the  advanced  practi- 
tioner that  some  method  is  demanded  whereby  the  thousands 
of  good  roots  now  sacrificed  can  be  made  permanently  useful. 
Notwithstanding  the  great  revolution  wrought  by  machinery 
and  improved  appliances  for  filling  teeth,  so  few  are  the  suc- 
cesses that,  unless  some  plan  is  brought  to  our  aid  to  save  the 
remaining  roots  from  the  ravages  of  decay  and  from  a  want  of 
skill  and  judgment  by  three-fourths  of  the  dentists,  we  shall 
have  little  else  than  plates  with  which  to  meet  the  issue.  Teeth 
can  be  saved  without  filling  as  well  as  by  filling  by  some 
operators,  but  by  a  few  only.  Most  of  the  dilemmas  which  all 
of  us  encounter  every  day  are  the  results  of  bad  dentistry.  The 
plan  to  meet  the  difficulty  must  be  one  which  is  founded  on 
such  mechanical  and  physical  laws  that  it  can  be  safely  relied 
upon  for  resisting  both  time  and  the  various  surrounding  cir- 
cumstances; one  which  any  ordinary  operator  can  follow,  and 
which  will  be  so  cheap  as  to  bring  it  within  the  reach  of  all; 
one  which,  if  by  accident  the  porcelain  crown  has  been  frac- 
tured, will  allow  of  easy  substitution  in  a  few  minutes  without 
interfering  again  with  the  operation  performed  on  the  root.  A 
crown  is  needed  which  can  be  obtained  by  every  operator  as 
easily  as  porcelain  teeth  for  plate  work,  and  kept  in  stock  by 
him  ready  for  any  emergency,  and  costing  but  a  trifle  to  replace; 


PIYOTIXG   ARTIFICIAL   CROWXS.  173 

a  method  by  which  we  can  take  any  case  of  great  irregularity, 
of  any  age  and  standing,  and,  without  disturbing  the  root,  cut 
oiF  the  crown  and  place  the  porcelain  one  in  the  proper  curve 
in  the  arch  ;  a  result  which  is  absolutely  clean,  and  which  will 
make  the  patient  feel  safer  from  accident  than  any  other  pro- 
cess of  restoration. 

"  Has  any  such  plan  been  generally  practiced?  A  few  have 
been  successful  by  certain  elaborate  methods  which  only  the 
exceptionally  skilful  could  perform,  and  even  then,  when  a 
'  break-do^v•n '  came,  there  was  no  alternative  but  to  do  it  all 
over  again,  either  at  the  cost  of  patient  or  operator. 

"  Since  1871  I  have  been  experimenting  in  this  direction. 
The  grand  object  in  view  was  to  give  to  the  dentist  at  large 
such  a  made-up  all-porcelain  tooth  as  would  meet  almost  any 
requirement. 

"My  first  jilan  (see  Dental  Cosmos,  September,  1877)  of  a 
bolt  and  nut  planted  in  the  root  by  gold  foil  did  not  succeed, 
as  the  safety  of  the  whole  depended  on  the  perfect  rigidity 
of  the  bolt.  Gold  could  not  be  so  packed,  save  in  a  few  cases. 
Amalgam  overcame  this  difficulty,  a  platinum  bolt  being  used 
instead  of  a  gold  one ;  but  this  operation  was  practicable  only 
to  skilled  mechanicians ;  the  average  dentist  was  unable  to  per- 
form it. 

"  To  meet  this  issue,  the  all-porcelain  crown,  without  nut, 
was  devised.  In  looking  at  the  incisor  crowns,  superior  and 
inferior,  one  might  suppose  that  with  so  much  cut  away  from 
their  base,  and  with  the  pin-hole  running  entirely  through  the 
crown,  the  strength  would  be  impaired.  So  I  feared  when  the 
idea  was  first  suggested  to  my  mind.  But  upon  trial  the 
strength  was  found  entirely  sufficient.  The  experiments  were 
made  Ijy  drilling  out  old-style  pivot  teeth  with  a  diamond. 
They  are  now  made  by  the  Trustees  of  S.  S.  White  in  special 
moulds.  With  these  still  greater  strength  is  attained.  The  in- 
cisors are  so  shaped  as  to  form  a  dovetail,  which  allows  the 
strain  outward  t<j  come  high  up  near  the  cutting  edge,  and  not 
to  depend  upon  the  palatal  base  for  support.     The  bicuspids 


174  MECHANICAL   DENTISTEY. 

and  molars  are  cut  out  at  the  base,  leaving  a  little  more  than  a 
shell,  with  undercuts  for  the  amalgam  to  act  as  dovetails. 

"  This  method  leaves  no  joint  on  the  natural  root,  and  none 
in  the  crown,  the  operation  being  really  an  amalgam  filling 
capped  with  porcelain.  The  hollow  crown  enables  the  opera- 
tor to  fit  it  in  a  very  brief  time,  there  being  but  little  material 
to  grind  oif. 

"  If  a  fracture  occurs,  a  new  crown  can  be  placed  with  but 
little  fitting  on  to  the  old  amalgam  base,  first  burring  oif  any 
excess.  When  a  case  is  presented  where  the  pulp  is  not  ex- 
posed, the  hollow-base  crown  permits  of  so  shaping  the  root  as 
not  to  endanger  the  pulp,  and  to  place  the  pins  on  either  side  of 
the  same  into  solid  dentine.  At  this  time  I  cannot  conceive  of 
a  single  case  occurring  that  cannot  be  met  by  one  or  the  other 
of  the  plans  herein  described  and  shown  clearly  in  the  cuts, — 
equally  adaptable  where  a  number  of  roots  are  in  continuous 
circle,  or  at  intervals,  or  even  for  a  full  denture,  as  the  teeth 
one  by  one  give  way  ;  or  in  making  the  root  of  a  lateral  bear 
the  crown  of  a  central,  or  vice  versa  ;  or  one  or  two  adjoining 
crowns  where  no  roots  are  left.  Where  more  than  one  crown 
is  needed,  the  nut  and  bolt  are  called  for,  as  in  case  of  accident, 
or  the  necessity  for  readjustment,  they  can  be  unscrewed,  the 
fixture  removed,  repaired  in  the  laboratory,  and  again  screwed 
in  place. 

"  Let  me  say  just  here  that  this  plan  of  nut  and  bolt  is  ap- 
plicable where  no  roots  are  present,  for  fastening  one  or  more 
plate-teeth  on  a  plate  instead  of  by  the  method  of  Dr.  Bing,  in 
which,  if  the  teeth  are  broken,  they  cannot  again  be  readjusted. 
Such  bolts  with  threads  cut  upon  them  can  be  inserted  in  any 
part  of  a  perfect  crown  or  a  filled  one  by  the  use  of  amalgam, 
or  gold,  if  one  will  use  it  in  such  cases. 

"  Next  in  importance  to  a  crown  that  will  meet  all  cases  are, 
the  bolt  which  is  intended  to  attach  it  to  the  root  or  roots,  and 
the  cement  for  securing  it. 

"  In  such  cases  as  are  outlined  in  Figs.  59  and  60,  see  that 
the  platinum  pin  is  secure,  and  so  placed  where  occasion  de- 
mands that  the  lower  part  of  the  root  need  not  be  filled  with 


PIVOTING   ARTIFICIAL   CROWNS.  175 

cement,  but  that  space  be  left  for  gases  to  escape  through  the 
tap-hole,  which  should  be  made  obliquely  from  near  the  margin 
of  the  gum  down  below  the  cement,  guarding  against  the  liability 
of  decay  again  occurring  at  the  cervical  margin  by  bevelling 
well  the  mouth  of  the  cavity  in  the  root.  This  once  done  cor- 
rectly, there  will  be  no  need  of  again  disturbing  it.  (Before 
setting  the  pin  in  any  case  the  root  should  be  temporarily  filled 
at  the  apex  to  insure  against  abscess.)  Cases  will  present, 
however,  where  gases  will  form  and  escape.  Here  perfect  se- 
curitv  can  be  obtained  by  the  tap-hole,  as  before  described. 
This  left  open  a  useful  root  is  retained,  and  without  any  ap- 
parent unpleasant  odor.  Do  not  condemn  an  abscessed  root. 
Such  can  be  made  equally  successful  where  the  periosteum  can 
be  restored  to  health.  Save  every  old  root  that  has  any  length, 
and  in  which  the  pin  can  be  well  anchored  high  up,  even  if 
the  walls  are  fractured  for  an  eighth  of  an  inch  below  the  gum, 
or  even  where  the  root  is  split.  In  such  cases  dovetailed  holes 
can  be  made  in  each  fractured  part,  and  the  amalgam  will 
hold  them  together.  Even  without  this  if  the  pin  have  a  good 
quarter-inch  anchorage  at  the  very  apex  it  will  be  hard  to  dis- 
lodge. 

"  To  make  doubly  sure,  when  a  tap-hole  has  to  be  made, 
that  it  is  open  from  the  apex,  pass  a  fine  thread  of  silk  or 
cotton  down  alongside  of  the  pin,  build  up  the  amalgam 
around  it,  withdrawing  it  after  the  crown  is  on  and  before  the 
amalgam  has  set,  holding  the  crown  firmly  while  doing  it. 
Or  the  thread  can  be  introduced  through  the  tap-hole  and  then 
passed  up  to  the  apex,  withdrawing  it  when  the  crown  is  in 
place.  This  practice  is  perfectly  justifiable  rather  than  to  lose 
a  serviceable  root.  To  a  conscientious  operator  it  needs  no 
argument.  In  a  very  important  root  I  go  so  far  as  to  allow  or 
even  to  force  an  abscess  to  form,  and  then  treat  it  through  the 
pulp-canal  and  fistula.  I  save  seventy-five  per  cent,  of  such 
cases  rather  than  abandon  them. 

"  Do  not  cut  away  the  root  very  much,  as  a  trifling  space  around 
the  three-cornered  pointed  pin  will  permit  enough  cement  for 
strength.     Roughen   the   inner   walls  of  the  pulp-canal,  and 


176  MECHANICAL   DENTISTEY. 

they  may  be  left  conical  without  clanger  of  the  pin  being  with- 
drawn. One  very  great  satisfaction  to  the  patient,  as  well  as 
to  the  operator,  is  that  the  rubber-dam  need  never  be  used. 
The  base  of  the  root  can  be  so  prepared  with,  a  sharp  bur  that 
but  little  injury  is  done  to  the  gum,  and  if  it  bleeds  creasote  or 
chloride  of  zinc  will  stop  it ;  or,  pressure  of  the  thumb  and 
index-finger  against  the  buccal  and  palatal  walls  will  stop  it 
or  any  serous  discharge  while  the  root  is  being  filled  with  ce- 
ment. After  that  there  is  nothing  to  hinder  the  placing  on  of 
the  crown.  Be  sure  before  forcing  in  the  amalgam  or  cement 
that  the  apical  foramen  is  closed.  For  this  purpose  I  use  fine 
zephyr  saturated  with  creasote,  except  in  cases  were  a  tap-hole 
has  to  be  made. 

"  Only  in  cases  of  fracture  of  the  shaft  of  a  root  would  I 
use  a  band,  and  that  should  be  placed  on  separately  from  the 
crown,  not  with  it.  Not  a  half  dozen  times  in  nine  years  have  I 
had  occasion  to  use  such  a  band.  The  use  of  the  platinum  pin  in 
the  pulp-canal  and  passed  high  up  obviates  any  necessity  for 
such  band,  which  is  at  best  unsightly,  and,  for  many,  other 
reasons,  objectionable.  Such  a  plan  admits  of  no  readjust- 
ment, and  has  been  used  by  others  only  to  assist  the  cement  in 
setting.  Cases  occur  where  each  root  of  a  molar  or  bicuspid 
stand  separated.  One  small  pin  in  each  well  pressed  up  gives 
equally  good  results. 

"  Never  depend  upon  cutting  a  female  thread  in  the  dentine 
and  placing  a  screw  therein.  This  can  be  done,  but  it  is  so 
easy  to  be  deceived  that  the  plan  as  shown  in  Fig.  58  is  much 
more  desirable  because  more  reliable.  It  is  preferable  in  such 
cases  to  place  in  the  pins  and  wait  until  the  next  visit  of  the 
patient,  and,  before  placing  on  the  crown,  to  try  the  pins  to 
see  if  they  are  well  anchored.  When  more  than  one  crown  is 
to  be  placed  on  in  a  continuous  circle  or  line.,  cut  off  all  the 
natural  crowns  at  one  sitting  instead  of  finishing  one  at  a  time 
as  I  once  advised.  As  many  as  four  incisors  can  be  inserted 
at  one  sitting,  though  two  is  as  much  as  one  generally  cares  to 
adjust  at  one  time.  Where  the  crowns  have  been  well  fitted 
to  a  plaster  model  there  will  be  little  difficulty  in  getting  a 


PIVOTING   ARTIFICIAL   CROWNS.  177 

good  arch  in  the  month,  though  a  model  is  not  necessary  ex- 
cept for  the  superior  or  inferior  incisors.  If  you  liave  a  large 
stock  of  bicuspid  and  molar  crowns  on  hand  the  fitting  can  be 
done  at  once.  For  special  cases  of  very  short  teeth  it  would 
be  well  to  have  a  plaster  model.  The  only  objection  ever 
urged  against  using  amalgam  in  the  roots  to  secure  tlie  pins  is 
that  the  gums  soon  look  purple  or  blue.  This  can  only  occur 
where  the  joint  is  not  high  enough  above  the  margin  of  the 
gum  and  where  poor  amalgam  is  used.  Oxyphosphate  or 
oxychloride  of  zinc  can  be  used,  but  I  prefer  a  special  quick- 
setting  amalgam  such  as  I  am  using.  Gutta-percha  for  such  an 
operation  is  no  better  than  putty.  Some  cases  have  succeeded 
with  its  use,  but  it  does  not  at  all  meet  the  requirements. 

"  As  to  the  oljjection  against  amalgam  that  it  is  too  plastic 
and  too  long  in  hardening,  let  me  say  that  in  fact  such  is  not 
the  case,  unless  the  ordinary  amalgam  is  used.  I  have  never 
had  to  replace  in  a  single  case  from  such  cause,  where  the 
amalgam  I  have  adopted  is  used  in  the  crown.  For  the  roots, 
any  first-class  amalgam  will  do  that  does  not  take  too  long  to 
set.  The  safety  is  in  having  it  not  too  soft  in  the  crown  when 
it  is  pushed  home.  AVhen  the  platinum  pin  is  pressed  up  into 
the  root  with  forceps,  with  the  pin  resting  against  the  palatal 
wall  of  the  tooth  in  incisors,  there  is  no  displacement.  The 
pressure  made  on  the  crown  'squeezes'  out  all  surplus  mer- 
cury and  impacts  the  amalgam  well  around  the  pin,  and  with 
a  lump  of  it  well  pressed  or  pounded  with  small  points 
around  tiic  pin  in  the  crown  from  the  outside  orifice,  it  holds 
securely. 

"  When  amalgam  is  used,  the  shade  of  the  crown  should  be 
rather  lighter  than  if  a  white  cement  were  to  be  used,  as  the 
opacity  of  the  amalgam  adds  a  blue  tinge  to  it,  just  as  in 
plate  teeth  the  shade  is  made  darker  by  the  stay-plate,  after 
soldering. 

"  Fig.  55  shows  the  crown  of  a  superior  central  from  the 
palatal  surface,  the  base  cut  out  high,  and  with  another  coun- 
tersunk hole  near  the  cutting  edge,  and  undercut  on  the  mesial 
and  distal  walls,  to  allow  the  amalgam  to  grasp  the  body  of 

12 


178  MECHANICAL   DENTISTRY. 

the  tooth  well  up,  so  that  it  shall  not  depend  for  support  at 
the  base  only.  The  base  may  be  cut  away  after  the  amalgam 
has  hardened  and  the  crown  would  not  fall  off.  The  base  is 
countersunk  to  admit  of  easy  and  free  adjustment  of  the  pin, 
and  to  allow  of  a  large  body  of  amalgam  around  it,  making 
one  continuous  amalgam  filling  from  the  root  through  the 
crown,  with  no  joint  for  retention  of  food,  the  material  being 
stronger  tlian  the  porcelain.  The  opening  on  the  palatal  sur- 
face is  convenient  as  a  safety  outlet  for  the  amalgam,  and  per- 
mitting the  crown  to  go  up  to  its  place  without  obstruction. 
When  the  crown  is  well  pressed  up,  the  amalgam  can  be 
packed  in  around  the  pins,  and  the  amalgam  will  act  as  a  me- 
tallic base  or  backing  for  the  palatal  surface,  thereby  strength- 
ening it.  The  thumb  or  index  finger  on  this  orifice  prevents 
the  too  free  escape  of  amalgam  when  pressing  up  the  crown. 


These  crowns  have  no  platinum  lining  or  tubes  as  the  English 
teeth  have.  They  are  stronger  without  them.  A  sectional 
view  of  a  central  is  also  shown  in  Fig.  55,  with  barbed  pin 
bent  at  the  proper  angle,  the  dark  part  showing  the  amalgam. 

"Fig.  56  shows  a  bicuspid  with  double  pulp-canal,  the 
cross-section  of  a  crown  with  countersunk  base,  and  the  open- 
ing on  the  grinding  surface  for  the  escape  of  surplus  amalgam. 

"  Fig.  57  embraces  sectional  views  of  a  superior  and  inferior 
molar,  showing  arrangement  of  pins,  with  a  magnified  view  of 
the  platinum  pin,  pointed  at  each  end,  made  triangular  and 
well  barbed,  the  barbs  looking  towards  the  angle  of  the  pin 
where  bent.  The  perfected  crown  on  the  root  shows  the  line 
of  amalgam.     When  two  or  more  pins  are  used  they  need  not 


PIVOTING   ARTIFICIAL   CROWNS. 


179 


be  placed  so  far  up  in  the  roots  or  be  so  large  in  diameter  as 
when  a  single  pin  is  used.  In  cases  where  the  root  has  to  be 
tapped,  then  the  pins  can  be  placed  in  the  mouth  of  each  pulp- 
canal  and  the  tap-hole  made  below,  which  should  always  be 
done  before  the  pins  are  inserted,  similar  to  Fig.  58,  where 
there  is  a  living  pulp.  Indeed,  were  it  not  for  the  fear  of 
displacement  before  the  hardening  is  complete,  pins  could  be 
dispensed  with  in  molars,  as  the  body  of  amalgam  is  so  great 


Fig.  56. 


Fig.  57. 


^ 


that  when  set  it  will  hold  sufficiently.  The  pins  when  set 
like  a  tripod  at  the  base  offer  greater  security  than  one  alone. 

"  Fig.  58  shows  an  all-porcelain  crown,  sectional  view,  where 
the  pulp  is  still  living.  A  hole  is  made  on  the  buccal  and 
lingual  sides  of  the  root  as  far  away  from  the  pulp-canal  as 
possible,  and  of  size  very  little  larger  than  the  three-cornered 
pin,  with  an  enlargement  near  the  opening  made  with  a  barrel- 
shaped  bur.  The  side  of  the  under-cut  next  to  the  crown 
should  be  as  square  as  possible,  not  rounded,  as  in  Fig.  58. 
In  such  a  case  the  amalgam  should  l)e  used  quite  dry,  as  the 
pins  do  not  have  to  be  pushed  far,  and  can  be  well  tamped  in 
with  narrow  steel  blunt  points,  so  as  to  make  sure  that  the 
amalgam  is  solid.  The  crown  can  be  placed  on  at  once,  or 
you  can  wait  until  the  next  day  to  see  that  the  pins  are  all 
secure. 

"  Fig.  59  is  a  sectional  view  of  a  case  that  requires  tapping. 
The  pin  shows  its  thin  flattened  edge,  with  space  on  either  side 


180 


MECHANICAL  DENTISTRY. 


for  gas  to  escape  from  the  foramen.     It  is  pressed  up  about 
three-fourths  of  the  length  of  the  canal. 

"  Fig.  60  illustrates  the  same  case  as  Fig.  59,  giving  a  view 
of  the  flat  side  of  the  pin  and  showing  its  bearing  on  either 
side  of  the  canal,  by  which  it  is  prevented  from  lateral  move- 
ment, the  same  as  if  the  amalgam  encased  it  all  the  way.  The 
gas  escapes  at  the  opening  at  A.  (This  opening  should  extend 
obliquely  up  to  near  the  free  margin  of  gum,  and  not  as  shown 


Fig.  58. 


Fig.  59. 


in  the  cut.)  The  amalgam  extends  no  further  into  the  root 
than  A.  This  plan  holds  good  in  any  tooth  of  one  or  more 
roots. 

"Fig.  61  shows  views  of  a  superior  central  incisor  crown  as 
made  from  a  plate  tooth  (pins  crosswise),  backed  up  with 
heavy  gold  plate  entirely  to  the  cutting  edge  and  down  to  the 
base  where  it  rests  on  the  root.  The  .shape  is  given  to  the 
palatal  surface  by  an  extra  plate,  struck  up  concave  with  a 
round  tool  on  lead  and  nicely  fitted  up  to  the  backing  on  the 
buccal  side,  extending  as  high  up  as  the  angle  or  about  up  to 
the  cross-pins,  and  filled  in  with  scraps  of  gold  plate  and  then 
soldered.  The  drilling  of  the  hole  through  the  base  and  the 
countersinking  on  the  palatal  side  are  done  with  the  engine. 


PIVOTING   ARTIFICIAL   CROWXS. 


181 


The  base  of  the  plate  tooth  should  be  cut  off  from  the  pins 
down  to  the  cervix  to  leave  more  room  for  the  nut.  The  nut 
ordinarilv  goes  nuich  closer  to  the  backing  than  is  shown  in 
the  sectional  view  of  Fig.  61.  The  pin  is  barbed  on  its  three 
sides  and  thread-cut  on  the  end  passing  through  the  crown. 
This  is  done  -with  the  ordinary  screw-plate  before  inserting. 
For  central  incisors  the  pin  of  platinum  wire  should  be  No. 
16,  and  for  small  lateral  No.  18.  The  nut  is  made  of  half- 
round  or  oval  gold  wire,  about  three  thirty-seconds  of  an  inch  in 
thickness.  The  hole  should  be  drilled  before  cutting  it  off 
from  the  main  piece,  and  a  female  thread  cut  in  it  by  a  tap 


made  of  an  old  excavator  filed  down  and  run  through  the 
hole  in  a  screw-plate  of  the  size  of  the  wire  to  be  used  in  the 
root.  The  slots  in  the  head  of  the  nut  should  be  crucial,  to 
admit  of  the  screw-driver  (Fig.  63)  being  used  at  each  quarter 
of  a  circle.  The  nut  should  be  tried  upon  the  threaded  part 
of  the  pin  before  being  finally  inserted,  to  see  that  no  mistake 
has  been  made  in  the  size  of  either  the  nut  or  pin.  Such 
mistakes  will  sometimes  occur.  The  pin  is  bent  slightly,  to 
allow  it  to  pass  through  the  hole  in  the  crown  and  stand  in 
the  countersink  equidistant  from  all  sides,  so  that  when  the 
nut  is  placed  on  it  it  will  bear  on  all  sides  of  the  countersink 
alike,  and  the  cn)wn  will  not  be  tipped  to  one  side.  The  pin, 
after  the  amalgam  lias  hardened,  can  be  bent  with  forceps  to 
suit  the  countersink,  tidving  care  not  to  bruise  the  thread.  The 
nut  cannot  be  placed  on  at  tlie  same  sitting,  as  the  amalgam 
will  not  be  hard  enough  to  justify  it. 


182 


MECHANICAL   DEJVTISTEY. 


"  If  SO  unfortunate  as  to  injure  the  thread,  repair  it  with  a 
little  screw-plate,  as  shown  in  Fig.  62.  This  may  be  made 
from  a  piece  of  steel  dividing-file,  cut  down  to  about  the  size 
shown  in  cut,  and  bent  at  right  angles  after  heating  it  to  a 
cherry  red,  and  afterwards  drilling  a  smaller-sized  hole  than 
the  pin,  through  the  short  angle,  and  tapping  it  with  the  same 
tap  used  in  making  the  gold  nut,  then  tempering  it  to  a 
dark  straw  color.  This  screw  plate  can  be  run  up  on  the  pin 
in  the  root,  and  recut  it  its  full  length  to  the  base.  This  ob- 
viates the  removal  of  the  pin  after  the  amalgam  has  set.  Taps 
and  plates  of  various  sizes  should  be  kept  on  hand  in  dupli- 
cates. 

"  Fig.  63  is  a  forked  screw-driver,  bent  at  right  angles  to 
admit  of  getting  into  the  palatal  surface  to  put  on  the  nut.    It 

Fig.  63. 


should  straddle  the  pin  and  be  only  wide  enough  to  cover  the 
diameter  of  the  nut. 

"  Fig.   64  shows  a  case  of  irregularity  which  was  beyond 
correction,  on  account  of  the  poor  character  of  teeth,  their  very 


Fig.  64. 


ugly  shape,  their  position  in  the  palatal  arch,  and  the  age  of 
the  patient.  In  such  cases  I  do  not  hesitate  to  cut  off  the 
crown,  destroy  the  pulp,  and  place  one  of  the  plate-tooth 


PIVOTING   ARTIFICIAL  CROWNS.  183 

crowns  with  a  nut.  To  do  so,  the  crown  must  be  connected 
to  the  root  by  a  strip  of  heavy  gold  plate,  extending  for  a 
quarter  of  an  inch  or  more,  to  bring  the  artificial  crown  into 
the  circle.  For  such  cases  the  all-porcelain  crown  will  not  do. 
The  teeth  can  be  separate  or  connected.     I  prefer  the  former. 

"  The  nut  and  bolt  is  best  where  a  crown  has  to  be  very 
long  and  there  is  a  close  ana  deep  underbite,  with  little  room 
for  the  crown,  without  being  too  full  in  front.  The  gold  back- 
ing gives  greater  security,  and  should  cover  the  whole  palatal 
surface  of  the  tooth.  There  are  other  special  cases  in  which 
this  plan  is  to  be  preferred,  but  only  for  superior  incisors  or 
cuspidati. 

''  This  plan,  as  before  suggested,  I  should  use  in  attaching 
one  or  more  teeth  on  a  small  plate,  where  the  roots  have  been 
lost,  securing  the  bolt  with  amalgam  to  either  decayed  or  sound 
crowns. 

*•'  In  this  plan  (Fig.  61)  the  pin  is  placed  in  the  same  as  for 
all-porcelain  crowns,  and  adjusted  before  it  is  set  to  suit  the  hole 
in  the  base  of  the  crown,  placing  gutta-percha  over  the  pin  in 
the  countersink  until  the  next  visit  of  the  patient,  when  it  is 
removed  and  the  gold  nut  placed  on.  All  excess  of  amalgam 
around  the  margin  of  the  gum  should  be  removed,  and  before 
placing  on  the  crown  finally  it  should  be  warmed  and  a  piece 
of  gutta-percha  stuck  on  to  the  base  and  pressed  up,  making 
a  water-tight  joint  when  the  nut  is  screwed  up. 

"  The  illustrations  are  so  accurate  that  it  seems  almost  un- 
necessary to  enter  into  any  detailed  direction  as  to  the  manner 
of  procedure ;  but  as  it  may  help  to  perfect  operations,  I  will 
do  so  in  few  words. 

"  The  root  or  roots  having  been  prepared,  and  in  readiness 
for  the  crowns,  the  canals  enlarged,  and  the  foramina  closed, 
the  platinum  pin  is  cut  off  rather  shorter  than  the  length  of 
the  root,  as  it  cannot  be  pressed  up  quite  its  full  length  through 
the  amalgam.  It  is  made  three-cornered,  and  pointed  at  either 
end — more  so  at  the  root  end — and  well  barbed  with  a  sharp 
knife,  as  shown  in  cut,  to  and  from  the  line  between  the  crown 
and  root,  and  bciiding  tlie  pin  so  that  it  shall  impinge  upon 


184  MECHANICAL   DENTISTEY. 

the  palatal  wall  if  for  an  incisor,  which  will  hold  the  crown 
firm  while  the  amalgam  is  setting. 

"  The  crown  having  been  adjusted  to  its  place  on  the  root, 
and  all  being  in  readiness,  the  canals  dry,  place  soft  amalgam 
entirely  up  to  the  end  of  the  canal,  and  when  full,  take  a 
pointed,  three-cornered  excavator  and  run  it  up  through  the 
amalgam,  to  force  a  way  for  the  platinum  pin.  This  latter  is 
placed  by  grasping  the  pin  with  a  pair  of  forceps,  and  gradu- 
ally pressing  it  up  as  far  as  it  will  go.  A  thin,  flat-pointed 
tool  can  now  be  used  to  condense  the  amalgam  about  the  pin. 
Before  this  is  done  the  crown  should  be  placed  on  to  see 
whether  the  pin  will  permit  it  to  assume  its  proper  place.  If 
not,  the  crown  can  be  forced  either  way,  and  the  pin  will  fol- 
low. The  tamping  around  the  pin  can  now  be  completed,  and 
an  excess  of  amalgam  placed  around  it.  The  crown  is  now 
filled  with  amalgam  and  grasped  between  the  thumb  and  in- 
dex-finger, and  pressed  hard  home.  The  opening  on  the  pal- 
atal side  of  the  crown  can  be  filled  with  hard  amalgam  and 
well  driven  up  about  the  pin,  leaving  a  surplus  for  dressing 
when  it  is  fully  hardened.  The  excess  of  mercury  is  pressed 
out  by  the  force  used  in  driving  it  into  place.  When  more 
than  one  pin  is  used,  they  can  be  filled  in  between  on  the 
grinding  surface,  and  wedged  apart  against  the  wall  of  the 
porcelain  tooth,  which  will  very  much  assist  in  retaining  them. 

"  This  can  be  done  all  at  one  operation,  although  the  pin 
can  be  placed  in  at  one  visit  and  the  crown  at  the  next.  Where 
a  crown  has  to  be  replaced  from  fracture,  cut  off  the  surplus 
amalgam  around  the  pin  with  the  engine  and  cutting-pliers 
until  the  new  crown  fits  nicely.  Fresh  amalgam  having  been 
laid  over  the  old  amalgam,  and  the  crown  pressed  up  as  be- 
fore, the  repair  is  complete.  The  crowns  are  not  made  to 
allow  of  their  being  pressed  up  over  the  end  of  the  root,  as  in 
the  Richmond  plan  of  a  gold  band,  as  there  is  no  necessity  for 
the  band,  save  in  the  few  instances  named  in  a  former  part  of 
this  article. 

"  As  to  many  little  details,  the  practitioner  can  improvise  to 
suit  every  case.     I  am  of  opinion  that  platinum  wire  is  the 


PIVOTING    ARTIFICIAL    CROWNS.  185 

best  for  the  pins,  although  steel  well  softened  will  do  if  entirely 
covered  with  amalgam.  The  cost  of  platinum  is  but  a  trifle 
more  than  the  steel,  and  with  it  there  is  no  danger  of  oxida- 
tion or  of  injury  from  the  mercury. 

"  I  give  this  plan  to  the  profession  with  the  assurance  that 
there  is  no  other  operation  in  dentistry  which  will  so  delight 
patients.  Instead  of  crowns  patched  up  with  gold,  amalgam, 
gutta-percha,  etc.,  you  have  in  this  plan  'art  concealing  art,' 
recommending  itself  to  the  common  sense  of  the  patron  and 
enabling  the  operator  to  get  well  paid  for  his  labor,  and  suit- 
ing itself  to  the  purse  of  eyery  class  of  society, — a  plan  which 
will  enable  us  to  blot  from  our  practice  in  a  great  measure  the 
necessity  for  dental  plates." 

What  is  known  as  Richmond's  method  of  attaching  artificial 
crowns  to  the  roots  of  teeth  is  applicable  to  bicuspids  and 
molars  as  well  as  to  single-rooted  teeth.  The  latter,  or  incisors 
and  cuspidati,  however,  are  porcelain-faced,  and  are  constructed 
and  fixed  in  the  following  manner : 

Prepare  the  root  in  all  respects  as  in  the  case  of  an  ordinary 
pivot  tooth.  Bevel  the  sides  of  the  dressed  end  of  the  root 
with  chisels  or  other  suitable  instruments  one-half  or  three- 
fourths  of  a  line  in  depth,  forming  parallel  walls  for  the  recep- 
tion of  a  narrow  gold  band,  which  is  subsequently  to  be  forced 
over  the  end  of  the  root  Take  then  a  narrow  strip  of  gold 
plate  (that  made  from  the  gold  pieces  coined  since  1860  being 
the  best  adapted  to  the  purpose)  about  24  gauge,  and  three 
lines  or  more  in  width.  AVith  round-nosed  pliers,  bend  this 
strip  so  as  to  encircle  the  end  of  the  root ;  mark  the  point  of 
junction  and  cut  off.  From  this  again  cut  off  from  one-six- 
teenth to  one-eighth  of  an  inch  according  to  the  size  of  the 
root,  and  unite  the  ends  with  solder  composed  of  gold  coin 
same  as  band  five  parts,  and  one  ))art  of  fine  brass  wire.  With 
files  or  corundum  disks  fashion  this  band  so  that,  while  it  is  of 
equal  width,  it  will  conform  to  the  marginal  contour  of  the 
dressed  end  of  the  root,  the  edge  of  the  band  underlying  the 
gum,  presenting,  when  finished,  an  antero-posterior  convexity 


186  MECHANICAL   DENTISTRY. 

and  lateral  concavity  corresponding  with  the  marginal  inequal- 
ities of  the  alveolar  processes. 

Bevel  the  outer  and  upper  edge  of  this  band,  and  force  it 
over  the  end  of  the  root.  Fit  a  gold  or  platinum  wire  pivot  to 
the  enlarged  opening  in  the  root  accurately,  but  not  so  tightly 
as  to  prevent  its  ready  withdrawal  on  gentle  traction,  and  long 
enough  to  j)roject  a  line  or  more  from  the  orifice.  With  the 
metal  pivot  in  place,  take  an  accurate  impression  of  the  parts, 
including  the  adjoining  teeth,  and  remove  carefully,  when  the 
metal  pivot  will  be  found  imbedded  in  the  wax  impression,  or 
if  not,  it  may  be  afterwards  removed  from  the  root  and  ad- 
justed in  its  proper  place  in  the  impression.  The  gold  band 
should  also  be  forced  from  the  root  and  placed  in  the  impres- 
sion. The  latter  should  then  be  filled  in  with  plaster  to  secure 
a» model  of  the  parts,  with  the  pivot  and  band  secured  in  their 
proper  relations.  Then  cut  and  fit  a  cap  of  thin  platinum 
plate,  perforated  to  pass  over  the  pivot  and  down  upon  the 
end  of  the  root,  or  within  a  little  distance  of  it,  leaving  some 
space  underneath  for  plastic  material  on  final  adjustment. 
This  platinum  cap  should  fit  into  the  gold  band  accurately. 
JSText,  select  and  adjust  a  suitable  plain  plate  tooth  to  the  space 
to  be  supplied  ;  remove  and  back  it  with  a  thin  plate  of  pla- 
tinum, and  rivet  or  bend  the  pins  to  secure  it  in  place.  Then 
readjust  it  in  its  i3roper  place  on  the  model,  and  secure  it  by 
adding  fresh  portions  of  plaster  and  sand,  building  it  up  over 
the  front  face  of  the  tooth  and  around  the  model. 

The  several  parts  are  thus  secured  in  their  proper  relations 
to  each  other.  When  the  investient  is  sufficiently  hard,  heat 
up  the  piece  slowly,  and  with  the  blowpipe  flow  in  upon  the 
parts  exposed  to  view  successive  portions  of  gold  solder,  com- 
pounded as  before  mentioned,  until  sufficient  has  been  added  to 
form  the  desired  posterior  contour  of  crown. 

The  piece,  when  properly  dressed  and  polished,  is  now  ready 
for  final  and  permanent  adjustment  to  the  root,  previous  to 
which,  however,  the  walls  of  the  root-canal  should  be  rough- 
ened or  grooved  somewhat,  and  the  wire  pivot  or  tube  barbed 
or  serrated. 


PIVOTING   ARTIFICIAL   CROWNS.  187 

Before  forcing  the  band,  with  tooth  now  attached,  over  the 
root,  introduce  into  the  enlarged  canal  of  the  root,  and  ai'ound 
the  base  of  the  crown,  sufficient  os-artificial,  phosphate  of  zinc, 
German  cement,  or  other  allied  plastic  material,  to  fill  completely 
all  vacuities  that  may  exist  around  the  wire  pivot  and  under- 
neath the  platinum  base  plate,  securing  by  this  means  increased 
attachment  and  stability  to  the  substitute.  To  permit  the  es- 
cape of  surplus  material  a  small  opening  may  be  made  with 
a  drill  through  the  posterior  face  of  the  crown  near  the  band, 
and  which  may  afterwards  be  closed  with  gold  foil.  When  in 
place  and  firmly  fixed,  the  lower  edges  of  the  gold  band  under- 
neath the  gum  should  be  forced  in  closely  upon  the  root  with 
burnishers. 

In  attaching  artificial  crowns  to  the  roots  of  bicuspids  and 
molars  by  this  method,  the  operation  is  simplified  some- 
what by  constructing  the  crown,  superficially,  exclusively  of 
gold  plate.  A  band,  of  the  quality  of  gold  before  mentioned 
in  connection  with  the  front  teeth,  equal  in  width  to  the  re- 
quired length  of  crown,  is  employed,  and  is  prepared  in  the 
same  manner  as  the  narrow  band.  The  end  of  this  gold  tube 
or  band  antagonizing  with  the  teeth  of  the  opposite  jaw  is  then 
closed  with  a  platinum  cap  fitting  into  it,  and  solder  flowed  over 
this  until  sufficient  thickness  is  provided  for  purposes  of  mas- 
tication, while  cusps  are  raised  by  adding  and  flowing  addi- 
tional pieces  of  solder  at  appropriate  points.  A  small  open- 
ing having  been  previously  made  for  the  escape  of  surplus,  the 
hollow  crown  is  filled  with  some  one  of  the  plastic  materials 
heretofore  mentioned,  and  the  crown  forced  over  the  root  and 
into  proper  position.  Increased  stability  and  firmness  of  at- 
tachment may  be  secured  by  fixing  serrated  gold  wires  in  the 
roots  before  placing  the  crown. 

The  following  method  of  substitution,  contributed  at  the  so- 
licitation of  the  author,  by  Professor  M.  H.  Chappell,  of  the 
Indiana  Dental  College,  though  similar  in  some  respects  to  that 
practice<l  l^y  Dr.  Richmond,  is  sufficiently  original  and  dis- 
tinctive in  its  main  features  to  warrant  its  introduction  in  this 
connection. 


188  MECHANICAL   DENTISTRY. 

Having  formed  and  fitted  a  gold  band  to  the  root  in  the 
manner  heretofore  described,  the  writer  continues :  "  Fit  the 
crown  to  the  root,  and  to  the  ferule  or  band ;  bevel  the  tooth 
at  the  gum  edge ;  dress  the  inside  of  the  band  to  a  sharp  edge, 
so  as  to  form  a  lap  joint  with  the  tooth ;  or,  if  preferred,  use 
diamond  disk  and  cut  shoulder  in  crown  to  receive  the  un- 
trimmed  edge  of  band. 

"The  pulp  or  pivot  canal  must  be  drilled  in  a  line  with  the 
palatine  surface,  so  that  the  plate  will  not  have  to  be  forged 
back  under  the  tooth.  The  canal  is  made  the  usual  size  and 
depth  for  pivot  teeth. 

"  A  backing,  of  the  same  quality  of  gold  as  the  band, 
soldered  to  a  thin  plate  of  platinum,  is  the  best.  Punch  or 
drill  holes  to  attach  the  tooth  pins ;  countersink  and  rivet  solid. 
Have  sufficient  plate  of  backing  to  form  the  pivot.  With  a 
fine  saw  or  separating  file  cut  in  each  side  at  base  of  tooth  one- 
third  way  off",  and  bend  in  the  edges  forming  a  tube  for  pivot. 
Solder  the  rivets  and  upper  part  of  tube  to  make  firm. 

"  The  tooth  and  ferule  are  now  ready  to  be  attached.  Dry 
the  mouth  and  root,  using  napkins  and  saliva  ejector.  Force 
the  band  over  the  root,  firm  and  perfect,  to  the  exclusion  of 
moisture.  Line  the  inside  of  band  and  end  of  root  with  gutta- 
percha, extending  it  down  the  canal.  Etch  the  tube  or  pivot 
so  that  the  beards  of  etching  touch  the  walls  of  pivot  canal. 
Fill  the  tube  of  plate  with  gutta-percha,  and  line  the  etched 
surface  and  end  of  crown.  Heat  the  artificial  crown  and 
gutta-percha  on  water-bath  pan,  and  with  warm  pliers  place 
the  tooth  in  position,  forcing  the  pivot  to  its  place.  When 
cool  burnish  the  band  or  ferule  to  root  and  crown. 

"Have  retaining-points  in  root  and  tube;  build  up  with 
gold  from  root  and  ferule,  to  give  the  proper  contour  of  the 
palatine  surface  of  the  natural  teeth.  After  polishing  the 
ferule  or  band  and  palatine  filling,  the  case  is  complete." 

Though  differing  very  materially  from  the  ordinary  methods 
of  pivoting  an  artificial  crown,  the  following  novel  manner  of 
supplying  the  loss  of  a  natural  tooth,  in  the  absence  of  the  root, 
and  without  the  intervention  of  a  plate  or  clasps,  may  properly 


PIVOTING   ARTIFICIAL   CROAVXS.  189 

be  classed  under  the  same  general  head.  The  original  concep- 
tion and  practical  application  of  the  process  is  ascribed  to  Dr. 
B.  J.  Bing,  of  Paris,  France.  Space  will  only  permit  the  in- 
troduction of  descriptions  which  relate  to  the-  more  recent 
modifications  of  the  method. 

Dr.  Marshall  H.  AVebb  thus  describes  his  method  of  oper- 
ating in  these  cases : 

"  The  insertion  of  a  crown  without  plate  or  clasps  where  no 
root  remains  is  a  difficult  operation,  but  when  well  performed, 
and  the  crown  attached  to  teeth  that  are  firm  in  their  sockets, 
it  is  both  satisfactory  and  permanent. 

"  The  first  such  operation  performed  by  the  writer  was  com- 
pleted February  12th,  1873,  and  the  crown  now  remains  as  firm 
as  when  inserted.  The  operation  Avas  performed  in  the  follow- 
ing manner :  After  suitabh'  forming  the  cavities  in  the  proxi- 
mate wall  of  each  tooth  next  the  space  left  by  the  loss  of  the 
one  tliat  had  been  extracted  (unnecessarily)  some  years  before, 
an  impression  of  the  parts  was  taken,  and  a  plain  porcelain 
crown  was  selected,  fitted  to  place  and  backed  with  gold  plate 
(18-k.).  A  portion  of  the  backing  extended  about  one  and  a 
half  lines  from  each  side  of  the  crown  for  insertion  in  the  cav- 
ities prepared  in  the  adjoining  teeth,  and  to  these  parts  a  gold 
wire  was  soldered  to  fit  into  the  pulp-chamber  of  the  central 
and  lateral  incisors.  A  small  gold  plate  was  then  formed  to  fit 
upon  the  gum,  covering  as  much  space  as  was  taken  up  by  the 
neck  of  the  natural  tooth.  When  the  backing  was  riveted  to 
the  pins  in  the  porcelain  and  this  placed  in  position,  and  while 
the  whole  rested  on  the  small  plate  upon  the  gum,  the  backing 
and  plate  were  so  secured  by  wax  that  they  could  be  removed 
intact,  and,  after  being  placed  in  a  matrix,  soldered.  Each  ex- 
tended side  of  the  backing  and  the  surface  of  the  wire  was 
barbed  with  an  engraver's  lossing  tool,  so  that  the  gold  foil 
would  the  better  secure  the  crown  when  filled  into  every  part. 

"  The  porcelaiU)  with  the  gold  attachments,  being  ready  for 
insertion,  a  piece  of  light  nicdiuni  rubber-dam  was  put  in  [)lace 
on  two  teeth  each  side  of  the  space  to  be  filled,  and  over  the 
gum  upon  which  the  crowii  was  to  rest.    (The  rubber  takes  up 


190  MECHANICAL   DENTISTRY. 

but  little  space,  and  this  is  more  than  compensated  for  when 
the  ligature — waxed  floss-silk — is  pressed  to  or  near  the  neck 
of  each  adjoining  tooth.)  Oxychloride  of  zinc  was  then  placed 
in  the  pulp-chamber  of  the  central  and  lateral  incisors  and  the 
crown  at  once  pressed  to  place.  When  the  cement  had  hard- 
ened sufficiently  to  safely  admit  of  further  progress  in  the  work, 
a  portion  of  it  was  cut  away  from  around  the  wire  so  as  to  make 
proper  aiichorage  for  the  gold.  Small  pieces  of  light  cohesive 
gold  foil  were  then  impacted  around  part  of  the  wire  and  that 
portion  of  the  plate  extending  into  the  cavities,  and  the  crown 
was  thus  secured.  The  porcelain  and  gold  attachments  as  pre- 
pared for  insertion  and  the  crown  in  position  are  illustrated  in 
Fig.  65. 

"  The  cavity  in  the  central  incisor  was  extended  to  the  cut- 
ting edge  of  the  toothy  that  access  might  be  had  to  the  wire  and 

Fig.  65. 


both  sides  of  the  plate ;  foil  could  not  otherwise  have  been  put 
in  place,  unless  a  portion  of  the  labial  margin  of  enamel  were 
cut  away,  and  this  would  have  been  objectionable  because  of 
the  exposure  of  gold.  A  small  part  of  the  labial  instead  of 
the  cutting  edge  of  the  enamel  of  the  lateral  was  removed,  for 
the  reason  that  there  is  not  such  a  body  of  tissue  as  to  safely 
allow  it  to  be  cut  away  to  the  same  extent  as  in  a  central  incisor. 
The  margin  of  enamel  was  so  formed,  and  the  foil  so  inserted 


PIVOTING   ARTIFICIAL,    CROWNS. 


191 


and  finished,  however,  that,  though  the  gold  can  be  seen,  it  is 
not  conspicuous. 

"AMiilethe  operation  just  described  has  thus  far  proved 
successful,  yet  there  is  a  possibility  of  the  porcelain  being 
broken  from  the  platinum  pins  which  hold  it  to  the  gold  plate. 
To  avoid  such  an  accident  a  groove  should  be  cut  on  each  side, 
and  along  the  cutting  edge  of  the  porcelain  (Fig.  49,  6),  that 
gold  foil  may  be  impacted  into  it,  after  a  heavy  backing  of 
gold  plate  and  the  wire  have  been  fixed  in  place  and  soldered. 
After  the  groove  has  been  cut  in  the  porcelain  with  a  fine- 
edged  corundum  disk,  one  with  an  edge  of  the  diameter  of  the 
gold  wire  selected  for  the  case  should  be  used  to  make  a  groove 
across  the  porcelain  between  the  pins  (Fig.  66,  «),  into  which 
the  wire  to  connect  the  artificial  crown  with  the  natural  teeth 
is  to  be  placed  (Fig.  66,  h),  either  beneath  the  plate  or  so  that 


Fig.  66. 


the  edges  of  the  latter  may  be  joined  to  it,  as  the  necessities  of 
the  case  may  require. 

"  A  starting-point  should  be  made  either  between  the  gold 
backing  and  porcelain,  or  between  this  and  the  wire,  and  the 
latter  firmly  fixed  in  a  hand-vise  while  the  gold  foil  is  being 
impacted  with  the  electro-magnetic  mallet.  When  the  gold  is 
properly  and  solidly  placed  in  the  groove  and  over  the  back- 
ing and  wire,  it  not  only  aids  in  securing  the  porcelain,  but 
the  contour  of  the  crown  can  be  nicely  filled  out,  and  the  op- 
eration made  durable  and  beautiful  (Fig.  67). 

"The  surface  of  the  gold  |)laccd  along  the  base  of  the 
crown  to  the  edge  of  the  porcelain,  and  which  is  to  rest  against 
the  gum,  together  with  the  palatal  portion,  ought  to  be  prop- 


192  •  MECHANICAL.   DENTISTEY. 

erly  formed  and  finished  before  the  crown  is  put  in  place,  and 
this  should  be  done  in  the  manner  before  described.  There 
should  be  a  little  space  between  the  wire  and  cervical  wall  in 
each  tooth  to  which  the  crown  is  to  be  attached,  and  narrow 
pieces  of  light  gold  foil  carefully  placed  in  this  part,  between 
the  wire  and  enamel,  with  small  curved  instruments,  and  with 
the  aid  of  the  mallet ;  the  surface  of  the  gold  at  this  part  at 
least  should  be  smoothly  finished  with  very  narrow  (,'g  in.) 
strips  of  fine  emery-cloth  before  the  rubber-dam  is  removed. 

"  In  cases  where  the  pulp  is  living  in  one  or  both  of  the 
teeth  to  which  an  artificial  crown  is  to  be  attached,  the  heavy 
gold  plate  or  the  wnre  must  be  so  arranged  as  to  fit  as  accurately 
and  to  be  made  as  secure  as  possible  in  the  cavities  prepared 
for  them.  In  some  cases,  and  where  the  form  of  the  cavity 
admits  of  it,  it  is  better  to  adjust  and  solder  a  small  gold  plate 
to  the  end  of  and  at  right  angles  with  the  wire  attached  to  the 
crown.  This  plate  should  be  so  formed  and  bevelled  that  gold 
foil  can  be  solidly  placed  over  the  surface  of  it  next  to  the 
artificial  crown,  and  into  the  groove  made  around  the  cavity 
in  the  dentine  along  the  boundary-line  between  this  tissue  and 
the  enamel.  When  all  is  in  readiness  for  the  operation,  oxy- 
chloride  of  zinc  should  be  placed  in  each  cavity  and  the  crown 
immediately  put  in  place,  and  very  carefully  held  there  till  the 
cement  has  so  crystallized  as  to  secure  the  ends  of  the  wire 
and  plate ;  about  an  hour  is  necessary  to  such  perfect  crystal- 
lization as  to  safely  admit  of  the  preparation  for  and  the  pack- 
ing of  the  gold  foil.  The  oxychloride  of  zinc  should  be  left 
between  the  little  plate  or  end  of  the  wire  and  bottom  of  the 
cavity,  and  all  parts  where  gold  cannot  well  be  placed ;  this 
preparation  also  protects  the  dentinal  fibres  from  thermal 
changes. 

"  One  of  the  most  satisfactory  operations  the  writer  ever 
performed  was  the  insertion  of  a  crown  where  a  cuspid  root 
had  been  extracted  (unnecessarily),  and  the  lady  subjected  to 
the  wearing  of  a  gold  plate  for  some  time.  This  crown  was 
prepared  and  the  contour  filled  out  with  foil  as  described  (and 
as  illustrated,  Fig.  67),  but  gold  wire,  No.  13,  was  attached  to 


PIVOTING    ARTIFICIAL    CROWNS. 


193 


and  built  in  with  the  porcelain,  and  placed  into  the  pulp- 
chamber  of  the  adjoining  lateral  incisor  (which  had  been  filled), 
and  this  same  wire  extended  from  the  anterior  to  near  the  pos- 
terior proximate  surface  of  the  first  bicuspid  tooth,  the  pulp  of 
which  remained  in  normal  condition.  The  crown  was  placed 
in  position  with  oxychloride  of  zinc,  and  cohesive  gold  foil 
was  then  impacted  with  the  electro-magnetic  mallet  around  a 
portion  of  the  wire  in  the  root  and  into  the  cavity  in  the  crown 
of  the  incisor,  and  also  into  the  cavity  in  each  proximate  wall 
of  the  bicuspid  tooth,  as  well  as  around  and  over  the  ware, 
joining  the  two  fillings  through  the  enlarged  fissure. 


Fig  68 


"  The  most  extensive  operation  of  attaching  a  crown  to  ad- 
joining teeth  was  performed  bv  the  writer  before  the  Pennsyl- 
vania State  Dental  Society,  at  Delaware  Water  Gap,  in  July, 
1879.  In  this  case  disintegration  had  taken  place  in  many  of 
the  teeth,  and  cavities  of  decay  had  been  prepared  and  filled 
from  time  to  time.  The  teeth  were  abraded  and  the  dentine 
was  exposed  along  the  entire  cutting  edge  of  each  tooth  that 
occluded  with  another.  The  right  upper  lateral  incisor  had 
Ijeen  hjst  twelve  years  before.  The  crown  of  the  left  cuspid 
tooth  was  missing,  and  but  a  small  portion  of  the  enamel  and 
dentine  of  the  first  bicuspid  upon  either  side  remained.    These 

13 


194  MECHANICAL   DENTISTEY. 

last  were,  of  course,  pulpless,  as  also  were  the  right  cuspid  and 
central  and  left  lateral  incisor  teeth,  and  the  pulp-chamber  of 
each  of  these  had  been  filled.  All  the  operations  made  neces- 
sary by  the  abrasion  and  fracture  of  enamel  from  time  to  time, 
and  because  of  imperfection  in  the  fillings  before  introduced, 
were  performed  previous  to  the  insertion  of  tlie  crown  in  the 
space  left  by  the  loss  of  the  lateral  incisor,  and  as  this  crown 
and  each  cavity  and  pulp-chamber  Avas  prepared  for  the  gold, 
all  appeared  as  here  illustrated  (Fig.  68).* 

"Gold  wire  (No.  13),  with  a  sharp  thread  cut  upon  it,  was 
screwed  into  the  dentine,  and,  at  the  same  time,  all  the  inter- 
stices between  the  tissue  and  the  gold  were  filled  with  oxychlo- 
ride  of  zinc.  When  crystallization  had  taken  place  some  of 
the  cement  and  dentine  was  removed  from  around  the  wire 
with  a  small  burr,  and  a  groove  was  cut  in  the  dentine  near  the 
margin  of  the  root  so  as  to  secure  proper  and  sufficient  anchor- 
age for  gold ;  cohesive  foil  (principally  No.  30)  was  impacted 
into  these  parts,  and  the  entire  contour  of  the  crown  was 
restored  with  the  electro-magnetic  mallet.  This  crown  was  not 
faced  with  porcelain,  because  the  teeth  of  the  gentleman  for 
whom  these  operations  were  performed  are  but  slightly  exposed 
to  view ;  and  then,  too,  the  gold  had  to  be  placed  over  the 
enamel  to  support  and  protect  it  along  the  cutting  edges  of  all 
the  incisor  and  the  cuspid  and  bicuspid  teeth.  A  gold  screw 
was  placed  in  the  pulp-chamber  and  extended  into  the  crown  of 
each  bicuspid  tooth  (Fig.  68).  The  apical  foramen  of  each 
pulpless  tooth  was  closed,  and  the  whole  of  each  pulp-chamber 
into  which  a  wire  was  not  placed  was  filled  with  gold.  With 
a  properly  adjusted  electro-magnetic  mallet,  carefully  guided, 
and  operated  with  a  full  current  of  electricity  from  a  freshly 
charged  four-cell  Bunsen  battery,  the  contour  of  each  crown 
was  restored  with  gold,  made  solid  g.nd  perfect  throughout; 
the  foil  was  placed  in  the  same  manner  over  the  finely  prepared 

*  The  cut  (Fig.  68)  illustrates  the  case  well,  though  there  are  parts  and 
grooves  in  which  to  anchor  the  gold  that  are  not  distinctly  shown. — M.  W.  H. 


PIVOTING   ARTIFICIAI^  CROWNS. 


195 


margins  of  enamel,  and   these  were  not  marred  in  the  least 
(Fig.  69). 

"  The  lower  incisor  teeth  had  so  changed  after  the  loss  of 
the  upper  lateral  that  they  almost  closed  upon  the  gum.  This 
was  partly  owing  to  the  abrasion  of  the  remaining  teeth,  and 
in  part  due  to  the  lower  incisors  gradually  rising  in  the  alveolar 
process.  Because  of  such  occlusion  of  the  teeth  a  porcelain 
crown   (plain  'plate  tooth')   with  'cross  pins'  was  used,  and 


Fig.  69. 


fitted  and  soldered  to  the  gold  wire,  there  being  no  space  for  a 
backing  of  plate.  When  the  wire  was  prepared,  the  porcelain 
grooved  and  fitted  to  it,  and  ready  for  the  placing  on  of  the 
gold  foil,  the  whole  appeared  as  illustrated  (Fig.  68) ;  the  wire 
extending  into  each  root  about  four  lines.  The  cutting  edge 
of  the  porcelain  was  removed  to  the  same  extent  as  that  of  the 
abraded  and  j)repared  incisors,  so  as  to  present  the  same  ap- 
pearance and  have  the  gold  support  and  protect  the  remaining 
part.  The  wire  of  the  crown  was  held  in  a  hand  vise,  while 
cohesive  gold  foil  was  placed  solidly  in  the  grooves,  around 
the  wire,  over  the  cutting  edge  of  the  porcelain,  and  the  entire 
contour  restored  with  the  electro- magnetic  mallet.  During  the 
final  fitting  of  the  crown,  it  was  made  to  so  rest  against  the 
gum  that  the  blood  was  pressed  from  the  capillaries  of  the  part. 
When  ready  for  insertion,  a  light  medium  rubber  dam  was  ap- 
plied to  two  teeth  each  side  of  and  across  the  space  which 
was  to  receive  the  crown  ;  'small  barbs  were  made  all  around 
the  wire  with  a  sharp  knife,  and  oxychloricle  of  zinc  was  then 
placed  in  tlic  pulp-chamber  of  the  central  incisor  and  cuspid, 
and  the  crown  at  once  pressed  to  place.     After  it  had  been  in 


196 


MECHANICAL   DENTISTEY. 


position  an  hour  to  allow  of  complete  crystallization  of  the  ce- 
ment, portions  of  this  and  of  the  dentine  were  removed  with  a 
small  burr  so  as  to  better  secure  the  crown  and  obtain  anchorage 
for  the  gold  foil  then  to  be  put  in  place  around  the  wire,  into 
each  cavity,  and  over  the  prepared  margins  of  enamel.  Prin- 
cipally No.  30  gold  (one-quarter  ounce  cohesive  foil)  was  used 
in  this  case,  and  all  was  impacted  with  the  electro-magnetic 
mallet,  except  a  few  pieces  of  light  foil  placed  in  the  space  be- 
tween the  wire  and  cervical  wall,  and  even  these  pieces  were 


Finisbt'd  Case. 

a,  6,  d,f,  g,  and  h,  pulpless  teeth  ;  g,  whole  crown  restored  with  gold  ;  a,f,  and  h,  almost 
entire  gold  crowns;  the  teeth,  b  and  d,  support  the  gold  crown  faced  with  porcelain,  c, 
and  fully  one-fourth  of  the  crown  of  each  of  these  is  restored  with  gold,  as  is  also  that  of 
e,  the  pulp  of  which  is  living. 

gone  over  with  this  very  valuable  instrument  after  they  were 
in  place.  With  this  and  all  the  operations  completed,  the  case 
appears  as  here  illustrated  (Fig.  70). 

"  All  those  who  have  the  ability  and  who  will  work  ear- 
nestly and  conscientiously  to  properly  perform  the  various  oper- 
ations described,  and  do  their  very  best  in  every  ease,  can  so 
manage  their  practice  as  not  to  make  it  necessary  for  any  of  the 
patients  they  have  charge  of  to  wear  artificial  crowns  mounted 
upon  plates." 


PIVOTING   ARTIFICIAL   CROWNS. 


197 


Professor  Darby,  in  commenting  on  this  method,  says : 
"  Dr.  B.  J.  Bing  was  the  first  to  call  my  attention  to  a 
method  of  building  one  tooth  into  the  adjoining  teeth  by  means 
of  gold  wires  running  from  the  artificial  into  the  natural  teeth. 
I  have  never  seen  any  of  Dr.  Bing's  operations,  but  Dr.  Mar- 
shall H.  Webb  has  called  my  attention  to  one  or  more  in  the 
mouths  of  his  patients,  which  have  done  good  service  for 
years.  I  also  have  in  my  own  ])ractice  one  or  more  which 
have  proved  most  satisfactory. 

"The  cuts,  Figs.  71  and  72,  represent  two  cases  where  arti- 
ficial crowns  have  received  their  support  from  the  adjoining 


Fio.  71. 


teeth.  It  is  desirable  to  have  a  pulpless  tooth  for  a  neighbor, 
though  I  question  if  one  would  be  justified  in  devitalizing  a 
pulp  to  secure  this  end.  In  the  cases  presented,  a  piece  of 
gold  wire  was  soldered  to  the  backing  of  the  porcelain  tooth, 


Fio.  72. 


and  allowed  to  extend  well  up  the  pulp-canal  of  one  of  the  ad- 
joining teeth.  After  it  had  been  nicely  fitted  to  its  place,  the 
rubber  dam  was  applied  and  drawn  tightly  over  the  gum  be- 
tween the  two  natural  teeth  ;  the  canal  of  the  devitalized  tooth 
was  then  filled  with  oxychloride  of  zinc,  and  the  tooth  with  its 


198  MECHANICAL   DENTISTRY. 

gold  support  pressed  into  position.  When  the  cement  had 
hardened,  the  bulk  of  it  was  cut  out  and  the  space  filled  thor- 
oughly with  gold.  The  other  end  of  the  bar  was  packed 
around  with  gold  foil,  and  the  cavity  of  decay  or  cavity  of  con- 
venience was  filled  in  the  ordinary  way. 

"  It  is  always  better  to  take  an  impression  of  the  space  and 
adjoining  teeth  at  the  outset,  and  then  do  the  major  part  of 
the  work  in  the  laboratory.  The  gold  wire  which  enters  the 
root  can  be  bent  or  shaped  with  the  pliers  when  the  patient 
presents  for  final  insertion. 

"  I  would  not  be  understood  as  saying  that  these  operations 
can  only  be  performed  successfully  where  there  is  a  devitalized 
tooth  for  a  neighbor ;  on  the  contrary,  I  have  seen  teeth  in- 
serted in  this  way  where  both  teeth  were  living,  but  the  sup- 
port which  is  to  be  derived  from  the  long  right  angle  of  gold 
in  the  root  is  certainly  a  great  security  against  accident,  add- 
ing, as  it  must,  great  strength  to  the  operation." 

If,  after  the  operation  of  ingrafting  an  artificial  crown,  in- 
flammation of  the  peridental  membrane  and  surrounding  struc- 
tures ensues,  active  measures  should  be  immediately  instituted 
for  its  reduction.  In  a  majority  of  cases,  active  suppurative 
inflammation  is  induced  either  by  shutting  up  an  habitual  dis- 
charge from  secreting  surfaces  at  the  apex  of  the  root,  or  by  a 
forcible  injection  of  the  air  contained  in  the  nerve  canal  into 
the  sensitive  tissues  beyond  the  apex  in  the  act  of  pressing  up 
a  tightly  fitting  pivot.  These  two  circumstances,  in  conjunc- 
tion, sometimes,  with  rough  and  unskilful  manipulation,  af- 
ford a  rational  explanation  of  the  needless  failures  so  common 
to  this  method,  and  enforce  the  necessity  of  first  radically  treat- 
ing any  existing  disease  in  the  appendages  of  the  root,  and  of 
afterward  filling  to  the  apex  before  introducing  a  pivot. 
Where  inflammation  results  from  the  injudicious  application 
of  the  pivot  as  just  stated,  it  will  ordinarily  be  sufficient  to  re- 
move the  latter  if  timely  application  is  made  by  the  patient  for 
relief ;  and  it  is  important  in  all  cases  to  instruct  the  latter  in 
reference  to  the  necessity  of  early  attention  to  any  disturbance 
that  may  accrue  from  the  operation.     Unavoidable  inflamma- 


PIVOTING   ARTIFICIAL   CEOWNS.  199 

tion  may  generally  be  aborted  by  the  timely  application  of 
some  active  connter-irritant  to  the  gum  directly  over  the  af- 
fected root,  or  by  local  bloodletting,  until  resolution  is  eifected. 
The  topical  remedies  will  sometimes  be  rendered  more  effective, 
especially  when  the  local  trouble  is  associated  with  an  inflam- 
matory diathesis  or  febrile  condition  of  the  system,  by  such 
constitutional  treatment  as  will  tend  to  diminish  or  equalize 
the  force  of  the  circulation. 


200  MECHANICAL   DENTISTRY. 


CHAPTER  VI. 

Partial  Dentures  retained  in  the  Mouth  by  Means 
OF  Clasps  attached  to  the  Natural  Teeth. 

Remarhs  on  the  Use  of  Clasps. — Clasps,  or  metallic  bands, 
have  been  long  and  very  generally  employed  as  a  means  of  re- 
taining parts  of  sets  of  teeth  in  the  mouth,  and  are  still  used 
for  that  purpose  by  many  practitioners.  When  these  appli- 
ances are  skilfully  adjusted,  and  all  the  conditions  pertaining 
to  the  mouth  and  remaining  natural  teeth  are  favorable  to 
their  application,  they  afford  a  certain,  permanent,  and  satis- 
factory means  of  supporting  partial  dentures,  and  may  be 
employed,  under  such  circumstances,  with  comparative  safety 
to  the  natural  organs.  When  it  is  remembered,  however,  that 
in  a  lamentably  large  proportion  of  cases,  clasps  are  carelessly 
or  unskilfully  formed  and  fitted  to  the  teeth  ;  that  the  organs  of 
support  are  often  indiscriminately  selected,  and  are  neither 
adapted  in  form,  situation,  or  structure  for  such  uses ;  and  that 
they  are  frequently  diseased  and  insecurely  attached  to  the 
jaw,  or  are  mutilated  for  the  reception  of  clasps,  we  can  readily 
understand  to  what  unlimited  extent  this  method  is  subject  to 
abuses.  In  fact,  no  other  special  process  in  mechanical  prac- 
tice has  been  so  fruitful  of  evil  as  that  under  consideration, 
and  the  opprobrium  which  but  too  justly  attaches  to  it  in  pro- 
fessional as  well  as  popular  estimation,  is  chargeable  more 
properly  to  bad  faith  and  unskilfulness  on  the  part  of  the 
operator,  and  to  want  of  attention  in  respect  to  the  cleanliness 
of  the  substitute  and  the  organs  of  the  mouth  on  the  part  of 
the  patient,  than  to  any  inherent  unsuitableness  of  the  method 
itself.  Nevertheless,  it  must  be  admitted  that,  under  the  most 
favorable  circumstances,  the  teeth  clasped  are  not  wholly 
exempt  from  liability  to  injury,  and  this  circumstance  in  itself 


CLASPS.  201 

renders  it  the  more  Imperative  that  the  process  should  be  sur- 
rounded by  all  the  safeguards  that  skill  and  ingenuity  can 
devise. 

The  opinion,  at  one  time  current,  that  the  injury  inflicted 
upon  the  teeth  by  clasps  was  mainly  the  result  of  mechanical 
action,  has  given  place  to  the  more  defensible  view  that  the 
causes  concerned  in  its  production  are  chiefly  of  chemical 
origin.  Thus,  the  secretions  of  the  mouth  with  j)articles  of 
alimentary  and  other  substances  being  retained  between  the 
clasp  and  tooth  for  a  sufficient  period  of  time,  and  exposed  to 
the  favoring  conditions  of  Avarmth  and  immobility,  suffer  a 
process  of  putrefactive  decomposition  by  which  acids  are  elimi- 
nated, and  which,  in  their  nascent  state,  act  with  perceptible 
energy  upon  the  bone  constituents  of  the  tooth,  producing 
decay.  The  rapidity  and  extent  of  this  action  will  depend 
much  upon  the  nature  and  quantity  of  the  acids  liberated ;  the 
structural  characteristics  and  vital  resistance  of  the  teeth ;  the 
mechanical  execution,  adaptation,  and  composition  of  the  plate ; 
and  the  personal  habits  of  the  patient  with  respect  to  cleanli- 
ness. 

The  most  usual  seat  of  decay  in  these  cases  is  at  the  neck  of 
the  tooth  where  the  enamel  is  thinnest,  and  is  sometimes 
limited  to  a  circumscribed  spot,  but  oftener  extends  on  a  line 
with  the  gum  involving  nearly  or  quite  all  of  that  part  of  the 
neck  of  the  tooth  embraced  by  the  clasp.  At  first  the  enamel 
becomes  bleached  and  softened  as  though  macerated,  and  is 
ordinarily  very  sensitive  to  both  chemical  and  mechanical  irri- 
tants. With  a  continuance  of  the  cause,  the  superficial  por- 
tions of  the  affected  parts  become  more  and  more  thoroughly 
disintegrated,  and  sooner  or  later  assume  the  open  form  and 
characteristics  of  ordinary  decay.  If,  as  was  formerly  sup- 
posed, decay  or  solution  of  tooth-bone  in  these  cases  resulted 
from  mechanical  attrition,  or  wearing  away  of  the  enamel,  the 
injury  would  Fjc  inflicted  at  points  distant  from  the  neck  of  the 
tooth,  wliere  the  clasp  lies  in  more  direct  and  immediate  con- 
tact with  the  protuberant  portions  of  the  crown ;  but  we  find 
that  decjiy,  from  this  cause,  is  not  only  of  infrequent  occur- 


202  MECHANICAL   DENTISTEY. 

rence  at  such  points,  but,  on  the  contrary,  the  enamel  here  is 
frequently  found  condensed  and  polished  by  the  mechanical 
action  of  the  clasp.  Certain  conditions  of  the  plate  and  clasp 
undoubtedly  favor  mechanical  action  and  accelerate  the  de- 
struction of  the  tooth ;  as  where  the  clasp  bears  unequally  with 
sharp  and  unfinished  edges  upon  the  tooth,  or  where  the  base 
is  faulty  in  its  adaptation  to  the  mouth,  admitting,  by  its 
mobility,  of  irregular  traction  or  pressure  upon  the  organs 
of  support.  Whenever  the  artificial  appliance  is  thus  unskil- 
fully constructed  and  applied,  and  free  interspaces  are  fur- 
nished for  the  lodgment  and  retention  of  particles  of  food,  and 
the  teeth  clasped  are  defective  in  structure,  and  we  have  con- 
joined with  these  an  utter  disregard  of  cleanliness  in  respect  to 
the  substitute  and  remaining  natural  teeth,  the  destruction  of 
the  latter  is  certain,  rapid,  and  generally  irretrievable. 

The  Teeth  to  which  it  is  most  proper  to  attach  Clasps. — The 
utility,  comfort,  and  appearance  of  a  partial  set  of  artificial 
teeth  in  the  mouth,  will  depend  much  upon  the  fitness  of  the 
natural  organs  selected  for  the  purpose  of  support.  "  A  clasp," 
says  Professor  Harris,  "should  never  be  applied  to  a  loose 
tooth,  or  to  one  situated  in  a  diseased  socket,  or  which  is  so  much 
affected  by  caries  as  to  render  its  perfect  restoration  and  per- 
manent preservation  impracticable,  and  when .  none  but  such 
can  be  had,  the  proper  course  to  pursue  is  to  extract  every 
tooth  in  the  jaw,  and  replace  the  loss  of  the  whole  with  an 
entire  upper  set.  The  application  of  clasps  to  diseased  or  loose 
teeth,  always  aggravates  the  morbid  condition  of  the  parts, 
and  causes  the  substitute  which  they  sustain,  to  become  a 
source  of  annoyance  to  the  patient.  Besides,  such  teeth  can  be 
retained  in  the  mouth  only  for  a  short  time,  and  when  they  give 
way,  the  artificial  appliance  becomes  useless,  and  even  while  it 
is  worn,  it  is  not  held  firmly  in  place,  but  is  moved  up  and 
down  by  the  action  of  the  lips  and  tongue,  so  that  its  presence 
can  hardly  escape  observation  from  the  most  careless  ob- 
server."* 

Teeth,  also,  that  are  too  short  to  admit  of  sufficient  breadth 

*  Principles  and  Practice  of  Dental  Surgery,  p.  717. 


CLASPS.  203 

to  the  clasp  to  impart  stability  to  the  substitute,  and  those 
that  stand  very  irregularly  in  the  arch,  rendering  it  difficult 
for  the  patient  to  apply  and  remove  the  appliance,  are  unsuit- 
able as  organs  of  support. 

In  respect  to  the  individual  classes  of  teeth,  it  may  l>e  ob- 
served that  the  incisors,  lx)th  as  regards  form  and  situation, 
are  inadmissible  for  clasping,  and  are,  therefore,  never  used 
for  this  purpose.  The  cuspidati,  likewise,  being  placed  con- 
spicuously in  the  front  part  of  the  mouth,  cannot  be  securely 
embraced  without  manifest  exposure  of  the  clasp ;  besides,  the 
conical  form  of  these  teeth  makes  the  use  of  a  very  slender 
clasp  indispensable ;  henc-e,  these  teeth  are  rarely  employed, 
and  may  only  be  used  when,  in  the  judgment  of  the  operator, 
the  necessities  of  the  patient  for  the  time  Ijeing  s^-em  to  require  it. 

Either  the  anterior  or  the  posterior  molars,  when  sound  and 
firm,  offer,  in  respect  to  their  general  conformation  and  posi- 
tion in  the  arch,  the  most  desirable  and  efficient  support  for 
parts  of  sets  of  teeth.  The  crowns  of  these  teeth  generally 
afford  ample  breadth  to  the  clasp ;  have  nearly  parallel  walls ; 
and  furnish,  by  the  strength  and  immobility  of  their  attach- 
ments to  the  Jaw,  the  greatest  security'  to  the  artificial  appli- 
ance. The  anterior  molars  are  preferable  where  these  are 
remaining  in  good  condition,  or  are  sasc-eptible  of  being  prop- 
erly restored  and  preserved  if  diseased  or  carioiK. 

Of  the  bicuspids,  the  posterior  are  to  be  selected,  if  practi- 
cable, as  these  better  favor  the  concealment  of  the  clasps ;  to 
effect  which  more  perfectly,  in  the  use  of  either  the  first  or 
second  bicuspids,  it  will  be  sufficient  in  many  cases  to  embrace 
only  the  posterior  half  of  the  crown. 

The  denies  sapientite,  or  wisdom  teeth,  will  seldom  admit  of 
the  application  of  clasps,  as  the  crowns  of  these  teeth  are 
usually  very  short  and  cone-shaped,  the  walls  converging 
abruptly  from  the  gum  ;  Ix-sides,  the  retractive  forces  applied  to 
the  anterior  teeth  of  the  substitute,  would,  on  account  of  the 
increased  leverage  consequent  upon  the  extension  of  the  plate 
back  to  these  teeth,  tend  either  to  disengage  the  clasps  or  pro- 
duce displacement  of  the  teeth  to  which  they  are  applied. 


204  MECHANICAL   DENTISTRY. 

In  supplying  the  loss  of  one  or  more  of  the  inferior  incisors, 
the  appliance  should,  as  a  general  thing,  be  attached  either  to 
the  anterior  or  posterior  bicuspids,  as  these  teeth  stand  more 
nearly  vertical  in  the  arch.  In  fixing  partial  lower  dentures^ 
it  will  be  sufficient  to  simply  provide  against  mobility  of  the 
base,  as  they  are  favored  rather  than  opposed,  as  above,  by 
gravitation.  The  replacement  of  the  inferior  teeth  posterior  to 
one  or  both  bicuspids,  however,  are  more  frequently  demanded  ; 
in  which  case  it  is  customary  to  attach  the  clasps  to  the  teeth 
immediately  in  front  of  and  adjoining  the  vacuities  on  each 
side.  It  will  not,  however,  be  necessary  to  attach  clasps  in 
these  cases  whenever  the  edentated  portions  of  the  jaw  present 
a  distinctly  scooped  form,  or  marked  concavity  of  outline, 
forming  a  kind  of  bed  for  the  plate.  If,  on  the  other  hand, 
the  ridge  falls  back  with  a  tolerably  uniform  inclination  from 
the  teeth  in  front,  with  no  sufficient  elevation  at  the  base  of 
the  coronoid  process,  it  may  become  necessary  to  provide 
against  backward  displacement  of  the  substitute  by  attaching 
clasps,  as  before  stated,  to  the  teeth  immediately  in  front.  In 
any  case,  if  the  dentes  sapientise  remain,  partial  or  stay  clasps 
may  be  attached  to  each  heel  of  the  plate,  and  so  adjusted  as  to 
rest  against  the  anterior  face  of  these  teeth,  obviating  entirely 
the  necessity  of  clasps  in  front. 

Separation  of  the  Teeth,  by  Filing,  for  the  reception  of 
Clasps. — The  practice  of  separating  the  teeth  with  the  file  to 
provide  for  the  application  of  clasps  should  always  be  avoided 
if  practicable,  since  the  liability  of  the  teeth  thus  denuded  of 
enamel  to  decay  is  greatly  increased  under  circumstances  so 
favorable  to  their  disintegration.  In  the  case  of  young  sub- 
jects, especially,  where  the  teeth  are  but  imperfectly  consoli- 
dated, and  in  adults  whose  teeth  are  defectively  organized,  pre- 
senting but  a  feeble  resistance  to  the  disorganizing  agents 
usually  present  in  the  mouth,  the  use  of  the  file,  for  the  pur- 
pose indicated,  is  eminently  pernicious,  and  should  never  be 
resorted  to  until  every  other  means  of  supporting  the  artificial 
appliance  have  been  fairly  and  patiently  tried. 

Whenever  a  plain  necessity  for  this  operation  exists,  a  care- 


CLASPS.  205 

ful  examination  of  all  the  teeth  to  which  it  is  proper  to  ap- 
ply clasps  should  be  made,  and  if  decay  is  found  upon  their 
proximate  surfaces,  the  separation  should  be  made  between  the 
teeth  so  affected  ;  and  this  circumstance  should,  in  most  cases, 
determine  the  selection,  though  the  affected  tooth  or  the  one  ad- 
joining may  not  be  esteemed,  in  other  respects,  the  best  for  the 
purposes  of  support.  If  decay  exists  on  the  proximate  surface 
of  only  one  of  the  teeth  to  be  separated,  a  safe-sided  file  should 
be  employed,  and  the  filing  confined  entirely  to  the  carious 
tooth,  leaving  the  enamel  of  the  one  adjoining  unbroken.  The 
cavity  of  decay  should  be  well  filled,  and  the  filed  surface 
thoroughly  condensed  and  polished  with  a  burnisher. 

Modifications  in  the  Form  of  Clasps. — 1.  Plain  Band.    The 
most  usual  form  of  clasp  is  that  shown  in  Fig.  73.    It  consists 


of  a  plain  metallic  band  of  greater  or  less  width  and  thickness, 
and  is  made  to  embrace  the  larger  portion  of  the  circumfer- 
ence of  tiie  tooth.  In  respect  to  the  general  properties  of  metal- 
lic clitsi)s,  it  may  be  said  that  they  should  be,  as  nearly  as  prac- 
ticable, of  the  same  quality  or  fineness  as  the  plate  or  base  to 
which  they  are  united ;  they  should  be  heavy  enough  to  impart 
adequate  security  to  the  attachment,  say  twice  the  thickness  of 
the  base,  and  exceeding  this  in  some  cases;  and  sufficiently 
elastic  to  embrace  accurately  the  more  contracted  parts  of  the 
teeth  after  having  been  temporarily  forced  apart  in  passing 
over  the  enlarged  portions  of  the  crowns.  In  constructing  a 
plain  band  or  clasp,  a  strip  of  sheet  lead  or  other  pliable  sub- 
stance may  first  be  fitted  accurately  to  the  plaster  tooth,  mak- 
ing it  of  tiie  rerpiired  width,  and  shaj)ing  the  edge  next  the 
gum  in  conformity  with  the  irregularities  in  the  latter  around 


206 


MECHANICAL   DENTISTRY. 


the  neck  of  the  tooth  ;  the  exact  counterpart  of  the  pattern 
thus  obtained  is  then  cut  from  the  plate  to  be  used  in  the 
formation  of  the  clasp.  The  strip  thus  obtained  is  then  bent 
with  round-nosed  or  grooved  pliers  (Fig.  74),  until  conformed 
as  perfectly  as  possible  to  every  portion  of  the  surface  of  the 
tooth  embraced  by  it.  This  coaptation  should  be  sufficiently 
accurate  to  exclude  perfectly  all  solid  substances  from  between 
the  clasp  and  the  tooth.  A  more  accurate  adaptation  of  the 
clasp  may  be  secured  in  the  following  manner  :  First  secure  a 
pattern,  as  before  described,  and  by  this  cut  from  a  thin  strip 
of  platinum,  say  ISTo.  30  or  32  of  the  gauge-plate,  a  band  of 
the  required  size  and  form,  and  press  or  burnish  it  accurately 
to  the  form  of  the  plaster  tooth.     The  soft  and  pliant  condi- 


FlG.  74. 


tion  of  this  metal  will  admit  of  its  being  easily  adapted  to  any 
irregularities  upon  the  lateral  walls  of  the  tooth.  The  band 
thus  moulded  to  the  tooth  is  then  carefully  removed  from  the 
model,  or  the  mouth,  if  fitted  to  the  tooth  in  the  latter,  and  its 
central  portion  filled  with  a  mixture  of  plaster  and  sand  with 
a  small  metallic  wire  or  bar  passing  through  the  centre  to  sup- 
port it  while  soldering.  The  outer  or  exposed  surface  is  then 
smeared  with  a  mixture  of  borax,  and  small  scraps  or  frag- 
ments of  gold  plate  of  equal  fineness  with  the  main  plate,  are 
placed  at  intervals  and  fused  with  the  blowpipe  until  diffiised 
uniformly  over  the  surface.     Small  pieces  may  be  added  from 


CLASPS.  207 

time  to  time,  until  the  required  thickness  of  the  clasp  is  ol> 
tained.  The  piece  should  be  heated  uniformly  throughout  to 
induce  an  even  flow  of  the  gold  over  the  exterior  surface  of 
the  platinum  ring.  By  this  method  a  faultless  adaptation  of 
the  clasp  to  the  tooth  may  be  secured,  provided  the  form  of 
the  latter  is  correctly  represented  on  the  model.  In  all  cases 
where  the  plain  band  is  used,  it  should  be  made  as  broad  as 
the  tooth  will  admit  of,  as  a  clasp  so  formed  gives  greater  sta- 
bility to  the  plate,  and  does  not  endanger  the  tooth  clasped  in 
any  greater  degree  than  a  narrow  one. 

2.  Standard  Clasp. — To  guard  more  perfectly  against  the 
retention  of  vitiated  secretions  and  particles  of  food  around  the 
neck  of  the  tooth,  a  method  of  constructing  clasps  has  been 
devised  and  introduced  to  the  notice  of  the  i>rofession  by  Dr. 

Fig.  75. 


C  W.  Spalding,  which,  by  leaving  the  cervical  portion  of 
the  tooth  in  a  great  degree  uncovered,  permits  the  action  of 
the  tongue  and  the  natural  circulation  of  the  fluids  of  the 
mouth  to  wjish  or  cleanse  that  portion  of  the  tooth  most 
liable  to  be  injuriously  aflected.  In  commenting  on  this 
method,  Dr.  S.  remarks :  "  The  writer  has  for  many  years 
been  in  the  habit  of  employing  narrow  clasps  for  the  pur- 
poses of  support,  making  them  of  sufficient  thickness  to  give 
the  required  strength,  and  attaching  them  to  the  plate  by 
means  of  standards,  so  arranged  as  to  induce  tlie  removal  of 
accumulations  between  the  clasp  and  tooth,  by  the  circulation 
of  the  saliva  (Fig.  75).  The  use  of  one  or  more  standards 
as  a  means  of  attachment,  also  provides,  by  a  variation  of  their 
lengtli,  for  the  grasping  of  the  tooth  at  any  desired  point.  If 
the  tooth  Ls  long,  and  particularly  if  it  is  at  the  same  time  bell- 


208  MECHANICAL   DENTISTEY. 

crowned,  the  point  selected  should  be  toward  the  grinding  sur- 
face, as  far  from  the  gum  as  is  found  practicable.  If  the  tooth 
is  short  and  of  such  form  that  it  can  be  successfully  clasped 
at  no  other  point  than  that  near  the  gum,  the  plate  should  be 
cut  away  at  least  one  or  one  and  a  half  lines  from  the  tooth, 
and  standards  introduced  for  the  purpuse  of  promoting  circu- 
lation, by  affording  a  free  passage  for  the  ingress  and  egress  of 
fluids.  These  standards  should  also  be  narroto,  no  wider  than 
the  clasp  itself,  and  should  constitute  the  only  point  of  union 
between  the  clasp  and  plate.  Haf-round  wire  will  be  found 
to  be  a  very  convenient  article  for  making  clasps.  The  par- 
ticular form  of  the  clasp  is,  however,  immaterial,  if  it  is  both 
narrow  and  strong,"* 

3.  Scalloped  Clasp. — Somewhat  analogous  in  form  to  the 
clasp  just  described,  and  constructed  with  a  similar  design,  is 
the  one  recommended  by  Dr.  B.  T.  Whitney.  A  plain  band 
of  gold  is  fitted  to  the  tooth  in  the  manner  first  described, 
when  that  portion  of  it  next  the  gum  on  the  lingual  side  of 
the  tooth  is  scalloped  or  cut  away  in  the  form  of  a  semicircle 
or  arch,  the  ends  of  the  clasp  being  in  like  manner  narrowed 
sufficiently  to  relieve  them  from  contact  with  the  neck  of  the 
tooth.  The  intermediate  points  of  the  clasp  which  serve  to 
unite  the  latter  to  the  base  may  be  two  or  more  in  number, 
and  should  be  wide  enough  to  impart  adequate  strength  to 
the  attachment.  A  clasp  so  formed  and  applied  to  the  base 
will  present  very  nearly  the  appearance  of  the  standard  clasp 
as  represented  in  Fig.  75.  Dr.  W.  recommends  soldering  but 
a  single  point  at  first,  and  then  having  tried  the  plate  in  the 
mouth  and  adjusted  the  clasp  properly  to  the  tooth,  remove 
and  solder  the  remaining  point  or  points. 

4.  Partial  or  Stay  Clasp. — This  form  of  clasp,  instead  of 
embracing  the  tooth,  is  designed  to  steady  or  fix  the  substitute 
in  place  by  simply  resting  against  one  side  of  the  tooth  to 
which  it  is  applied.  (Fig.  76.)  They  should  be  so  connected 
to  the  plate  that  when  pressed  over  the  enlarged  portions  of  the 

*  American  Dental  Review,  vol.  i,  p.  12. 


CLASPS. 


209 


crowns  of  the  teeth,  they  will  spring  readily  into  place  and 
adapt  themselves  closely  to  the  more  contracted  parts  near  the 
gum.  In  cases  where  there  is  no  adequate  opposing  force  to 
that  exerted  by  the  clasp,  care  should  be  taken  that  no  more 
pressure  is  produced  than  is  necessary  to  keep  the  substitute  in 


Fig.  76. 


place,  as,  without  this  precaution,  outward  displacement  of  the 
teeth  is  liable  to  occur,  and  the  appliance,  losing  its  bearing 
upon  the  teeth,  soon  becomes  loosened  and  insecure  in  the 
mouth.  The  result  alluded  to  should  be  particularly  guarded 
against  in  the  case  of  young  subjects,  whose  teeth  are  easily 
moved  by  the  application  of  very  slight  forces. 

Modification  in  the  Form  of  Plates  for  Partial  Dentures 
supported  in  the  3fouth  by  Clasps. — The  particular  form  and 
dimensions  of  a  plate,  when  clasps  are  used,  will  be  mainly 


determined  by  the  number  and  position  of  the  teeth  to  be 
replaa;d,  and  by  tiie  location  of  the  natural  organs  to  which 
the  clasps  are  attached.  It  will  be  sufficient  in  this  place  to 
indicate  the  leading  forms  as  they  relate  to  the  substitution 

14 


210 


MECHANICAL    DENTISTRY. 


of  the  several  classes  of  teeth.  In  supplying  the  loss  of  a 
superior  central  or  lateral  incisior,  it  will  be  sufficient  in  many 
cases  to  attach  the  plate  to  either  a  bicuspid  or  molar  on  the 
same  side,  as  in  Fig.  77.  If  two  or  more  of  the  front  teeth, 
however,  are  to  be  replaced,  it  is  better  to  extend  the  plate  on 
each  side  of  the  palatal  arch,  and  attach  to  a  bicuspid  or  molar 


Fig.  78. 


Fig.  79. 


Ij>r— £|^> 


(Fig.  78) ;  or  to  a  bicuspid  on  one  side,  and  a  molar  on  the 
other;  unless  two  firm  and  well-formed  teeth  on  the  same  or 
the  opposite  side  can  be  commanded  (Fig.  79),  while  those  upon 
the  other  could  hot  be  employed  without  a  separation.     In  all 


cases  where  it  is  necessary  to  extend  a  narrow  plate  from  the 
extreme  front  part  of  the  mouth  to  a  single  tooth  situated  pos- 
teriorly in  the  arch,  the  former  should  be  strengthened  by 
soldering  a  narrow  rim  of  plate  or  half-round  wire  along  the 


CLASPS. 


211 


border  next  the  teeth,  and  the  clasp  should,  Avhenever  prac- 
ticable, pass  in  front  of,  and  embrace,  the  anterior  face  of  the 
tooth  to  which  it  is  applied. 

If  an  anterior  bicuspid  is  to  be  replaced,  the  plate  may  be 
attached  to  the  adjoining  bicuspid  (Fig.  80,  right  side),  or  if 
both  are  absent,  then  to  the  first  molar  (Fig.  80,  left  side), 
or  the  clasp  may  embrace  both  of  the  latter  if  remaining  and 
no  separation  between  them  exists.  Fig.  81  represents  the 
form  of  a  plate  supplying  the  loss  of  teeth  at  intervals;  the 
clasp  on  one  side  embracing  the  posterior  bicuspid  in  front 
and  extending  round  the  back  part  of  the  adjoining  molar. 

Fig.  82  represents  the  form  of  plate  supplying  the  loss  of 
the  two  bicuspids  on  one  side,  and  the  anterior  bicuspid  and 


Fig.  82. 


Fig.  83. 


molar  on  the  opposite,  the  plate  being  attached  to  an  anterior 
molar  and  second  bicuspid.  The  antero-posterior  extension 
of  the  plate,  as  exhibited  in  connection  with  the  bicuspid 
tooth,  greatly  favors  the  stability  of  the  substitute,  and,  pro- 
vided the  plate  and  clasp  are  accurately  fitted  to  the  parts,  the 
support  afforded  by  a  bicuspid  tooth  under  such  circumstances 
Is  equivalent  to  that  furnished  by  a  firm  and  well-formed 
molar  clasped  as  shown  on  the  opposite  side.  A  base  so  sup- 
ported may  be  made  to  sustain  any  number  of  teeth  with  the 
greatest  security. 

Either  the  anterior  or  posterior  molars,  if  firm  and  securely 
attached  to  the  jaw,  will  afford  adequate  support  to  a  ])late 
replacing  all  of  tlie  teeth  anterior  to  them.  (Fig.  83.)     Even 


212 


MECHANICAL   DENTISTRY. 


a  single  molar  situated  on  either  side  of  the  arch,  if  similarly 
circumstanced,  may  be  made  to  sustain,  with  tolerable  firm- 
ness, a  base  supplying  the  loss  of  all  the  remaining  teeth, — 
though,  ordinarily,  it  is  better  to  extract  such  a  tooth  and 
substitute  an  entire  upper  denture.  In  all  cases,  where  any 
considerable  number  of  teeth  anterior  to  those  clasped  are  to  be 
replaced,  and  a  vacuity  on  the  ridge  exists  posterior  to  the 
latter,  the  plate  should  be  extended  back  and  overlap  the 
ridge  (Fig.  84),  the  latter  affording  a  counter-point  of  resist- 
ance when  traction  is  made  upon  the  anterior  teeth,  thus  di- 
recting the  forces  applied  more  on  a  line  with  the  long  axes  of 
the  teeth  that  sustain  the  appliance. 

In  supplying  the  loss  of  the  inferior  molars  and  bicuspids, 
or  any  number  of  these  teeth,  the  form  of  plate  represented  in 


Fig.  84. 


Fig.  85  is  generally  employed.  The  parts  of  the  plate  over- 
lapping and  resting  upon  the  ridge  behind,  are  connected  with 
each  other  by  a  narrow  strip  of  plate  extending  round  the 
ridge  in  front  on  the  lingual  side  of  the  anterior  teeth.  This 
latter  portion  of  the  plate  should  be  accurately  swaged  to  the 
form  of  the  gum  on  which  it  rests,  and  should  be  made  narrow 
enough  to  avoid  encroaching  upon  the  reflected  portion  of 
mucous  membrane,  the  glands  beneath  the  tongue  or  the  frse- 
nura  linguae.  To  avoid  wounding  these  parts,  and  to  allow 
them  unobstructed  play,  it  will  be  necessary  to  make  this  por- 
tion of  the  plate  quite  narrow ;  and  as  a  single  thickness  of 


CLASPS.  213 

plate  would  not  impart  adequate  strength,  it  is  customary  to 
double  this  connecting  baud — the  duplicate  band  extending 
back  to  the  lateral  wings  of  the  plate,  and  crossing  them  ob- 
liquely, as  indicated  by  the  dotted  lines  in  Fig.  85.  Addi- 
tional strength  will  be  given  by  doubling  the  entire  plate,  but 
this  is  not  generally  required.  The  outer  border  of  those 
portions  of  the  plate  overlapping  the  ridge  may  be  turned  up 
to  the  depth  of  from  half  a  line  to  a  line  to  form  a  groove  or 
socket  for  the  reception  of  the  ends  of  gum  teeth,  or  blocks, 
if  such  are  used  ;  while  the  inner  margins  should  terminate  iu 
a  rounded  edge,  extending  from  heel  to  heel  of  the  plate,  this 
form  being  given  to  it  either  by  turning  the  edge  over  and 
filling  iu  the  groove  with  solder,  or  by  soldering  a  narrow 

Fig.  86. 


strip  of  plate  or  half-round  ware  along  the  border.  The  cir- 
cumstances or  conditions  which  make  the  use  of  clas2>s  neces- 
sary in  these  cases,  as  well  as  those,  also,  which  contraindicate 
their  employment,  have  already  been  noticed.  The  practice 
of  extending  a  narrow  band  or  wire  from  the  sides  of  the  plate 
round  the  outer  border  of  the  ridge  in  front  of  the  anterior 
teeth,  to  prevent  a  backward  displacement  of  the  base,  is  liable 
to  produce  irritation  and  tenderness  of  tlie  mucous  membrane 
immediately  over  the  roots  of  the  anterior  teeth,  and  should, 
therefore,  never  be  resorted  to,  unless  there  are  no  teeth  re- 
maining to  which  clasps  may  be  applied. 

If  tiie  appliance  is  designed  to  restore  the  loss  of  teeth  re- 
cently extracted,  and  where  but  little  or  no  change  has  occurred 
from  ab.sorj)tion  of  the  parts,  the  portions  of  the  j^late  which 


214  MECHANICAL,   DENTISTRY. 

pass  in  between  the  adjoining  teeth  should  terminate  a  line  or 
more  within  the  outer  circle  of  the  remaining  teeth ;  and 
where  the  space,  if  it  happens  in  the  front  part  of  the  mouth, 
admits  of  two  or  more  teeth,  the  edges  of  the  extended  portion 
of  plate  should  be  scalloped  in  correspondence  with  the  fes- 
toons of  the  gum,  as  seen  in  Fig.  S6.  In  such  cases,  plain  or 
plate  teeth,  by  which  is  meant  those  which  represent  only  the 
crowns  of  the  natural  organs,  should  be  employed ;  these,  rest- 
ing on  the  edge  of  the  plate,  will  overlap  somewhat,  with 
their  anterior  edges  resting  directly  upon  the  gum  in  front, 
taking  the  place  occupied  by  the  crowns  of  the  extracted  teeth. 
On  the  other  hand,  if  sufficient  time  has  elapsed  after  the  ex- 
traction of  the  teeth  to  permit  the  changes  in  the  form  of  the 
ridge  to  occur  incident  to  partial  or  complete  absorption  of  the 
parts,  and  a  greater  or  less  concavity  exists  between  and  above 
the  teeth  on  the  outside  of  the  jaw,  the  plate,  where  it  passes 
into  the  interspace,  should  extend  some  distance  over  the 
border  of  the  ridge. 

Swaging  or  Stcimping  the  Plate. — Haying  determined  upon 
the  proper  form  and  dimensions  of  the  plate  for  any  given 
case,  its  outlines  may  first  be  traced  upon  the  model;  from  this 
an  exact  pattern  in  lead  may  be  obtained,  or  the  pattern  may 
be  sufficiently  ample  to  partially  overlap  the  cut  extremities 
of  the  teeth  when  the  latter  are  not  represented  upon  the  die, 
having  been  previously  cut  from  the  model.  The  outlines  of 
the  pattern  are  then  traced  upon  the  plate  of  gold  or  other 
metal  to  be  used  for  the  base.  The  redundant  portions  of 
plate  are  then  cut  away  with  plate  shears  and  forceps,  and  the 
edges  trimmed  smooth  with  a  file.  A  very  convenient  and 
almost  indispensable  instrument  for  cutting  away  the  plate 
where  it  describes  the  palatal  curvature  of  the  teeth,  is  a  plate 
forceps,  as  exhibited  in  Fig.  87. 

The  plate  cut  to  the  proper  form  is  now  placed  upon  the 
die  and  brought  as  nearly  as  possible  into  adaptation  with  a 
wooden  or  horn  mallet ;  it  is  then  placed  between  the  die  and 
counter,  the  latter  resting  on  an  anvil  or  other  equally  resist- 
ing surface,  when  the  two  metallic  pieces  are  brought  forcibly 


CLASPS. 


215 


together  with  a  few  stearly  and  well-directed  blows  of  a  heavy 
hammer.  Tilting  of  the  die,  resulting  sometimes  unavoidably 
from  a  one-sided  blow,  may  be  obviated  by  placing  a  cone- 
shaped  piece  of  cast  iron,  brass,  or  zinc  over  the  die,  the  base 
of  the  cone  resting  on  the  back  of  the  die ;  by  this  expedient 
the  force  of  the  blow  is  equalized  and  concentrated  more 
directly  over  the  die.  The  metallic  swages  should  at  first 
be  brought  cautiously  together,  and  should  be  separated  after 
the  first  blow  or  two  to  enable  the  manipulator  to  detect 
and  remedy  any  malposition  of  the  plate  before  it  becomes 
intractable  from  continued  swaging.  If,  in  the  process  of 
stamping,  any  portion  of  the  plate  is  found  cracking  or  part- 
ing, its  further  extension  at  that  point  may  be  prevented  by 


Fig.  87. 


flowing  a  little  solder  at  the  termination  of  the  fissure.  Dur- 
ing the  progress  of  swaging,  the  plate  should  be  frequently 
annealed,  which  is  done  by  bringing  it  to  a  full  red  heat  under 
the  blowpipe,  or  by  j)lacing  it  in  the  furnace;  the  plate  is 
thus  rendered  more  pliant  and  can  be  more  readily  and  per- 
fectly forced  into  adaptation  to  the  irregularities  on  the  face 
of  the  die. 

If,  after  somewhat  protracted  swaging,  the  plate  is  not  con- 
formed perfectly  to  the  face  of  the  die,  another  and  unused 
counter  should  be  substituted  for  that  in  use;  and,  indeed,  it 
is  better  in  all  cases  to  have  duj)licate  copies  both  of  the  die 
and  counter  in  reserve  with  whit^h  to  complete  the  swaging, 
inasmuch  as  more  or  less  deformity  of  both  swages  unavoid- 
ably occurs   before  the  plate    is    brouglit   into  very  accurate 


216  MECHANICAL   DENTISTRY. 

coaptation  with  the  die.  The  stamping  conducted  thus  far,  the 
plate  may  be  applied  to  the  plaster  model,  and  if  found  too 
full  at  any  points,  it  should  be  trimmed  with  a  file  to  the  exact 
dimensions  required.  The  margins  of  the  plate  adjoining  the 
necks  of  the  teeth  should  be  permitted  either  to  lie  closely  to 
them,  or  should  be  cut  away,  leaving  a  space  equal  to  a  line  or 
more  between  the  plate  and  the  teeth  ;  for  if  but  a  very  nar- 
row line  of  uncovered  gum  remains  at  these  points,  injury  to 
the  parts  immediately  surrounding  the  necks  of  the  teeth  is 
more  liable  to  occur  from  strangulation  of  the  interposed  gum 
than  if  the  plate  were  further  removed  from  the  teeth  or  rested 
directly  against  them. 

If  the  portion  of  the  plate  which  passes  in  between  the  re- 
maining teeth  is  quite  narrow,  as  where  but  a  single  tooth  is 
to  be  supplied,  it  should  be  strengthened  by  wiring  the  edges  or 
doubling  the  plate  at  such  point.  It  is  also  advisable  in  many 
cases,  in  order  to  provide  more  perfectly  against  fracture  or 
distortion  of  the  base  in  mastication,  to  wire  or  double  the 
entire  border  of  the  plate  adjoining  the  necks  of  the  teeth. 
Narrow  bands  of  gold  resting  against  the  necks  of  the  teeth, 
constructed  and  adjusted  after  the  manner  of  stay  clasps,  are 
sometimes  soldered  to  the  edge  of  the  plate  next  the  teeth  ;  but 
unless  the  substitute  is  frequently  removed  from  the  mouth 
and  cleansed,  as  well,  also,  as  the  teeth  to  which  they  are  ap- 
plied, serious  injury  is  likely  to  be  inflicted  upon  the  teeth  im- 
plicated. 

The  edges  of  those  parts  of  the  plate  occupying  the  vacuities 
on  the  ridge  should  be  filed  thin  to  admit  of  a  more  accurate 
adaptation  of  the  artificial  with  the  natural  gum,  and  should 
not,  as  before  observed,  ordinarily  extend  beyond  the  outer 
circle  of  the  contiguous  teeth,  allowing  the  gum  extremity  of 
the  artificial  tooth  to  overlap  and  rest  directly  on  the  natural 
gum  above.  If,  however,  the  concavity  between  and  above 
the  teeth  on  the  external  border  of  the  ridge  is  considerable, 
the  interdentinal  portions  of  plate  should  overlap  the  border 
completely  and  underlie  the  porcelain  gum. 

Uniting  the  Plate  and  Clasps. — Having  proceeded  thus  far 


CLASPS.  217 

in  the  operation,  the  plate  and  clasps  should  next  be  united  to 
each  other,  and  the  utility  and  comfort  of  the  appliance  in  the 
mouth,  as  well  as  the  safety  of  the  natural  organs  used  for  the 
purpose  of  support,  will  depend,  in  a  great  measure,  upon  the 
accurateness  of  the  relation  of  the  several  parts  of  the  appli- 
ance to  the  organs  of  the  mouth  ;  it  being  a  matter  of  primary 
importance  that  the  various  parts  of  the  substitute  should  be  so 
adjusted  to  the  remaining  teeth, — especially  those  to  which  the 
clasps  are  applied, — and  the  ridge  and  palate,  that  it  shall  not, 
in  any  material  degree,  act  as  a  retractor  upon  the  organs  of 
support,  or  furnish  interspaces  for  the  lodgment  of  food,  Avhile 
at  the  same  time  it  should  be  so  fitted  as  to  be  easily  removed 
and  applied  by  the  patient. 

The  clasps  having  been  fitted  to  the  plaster  teeth  and  the 
base  swaged  to  the  form  of  the  palatal  arch  and  ridge,  the  plate 
is  placed  in  its  proper  position  in  the  mouth  and  an  impression 
in  wax  taken  of  the  latter  with  the  plate  in  place.  The  im- 
pression with  the  plate  adhering,  is  then  removed  from  the 
mouth,  its  surface  oiled  and  a  model  obtained  in  the  manner 
heretofore  described.  If,  in  separating  the  model  and  im- 
pression, the  plate  adheres  to  the  latter,  it  should  be  detached 
and  adjusted  to  the  model  and  the  clasps  arranged  upon  the 
plaster  teeth.  The  plate  and  clasps  may  now  be  bound  to  the 
model  with  annealed  wire,  and  united  to  each  other  with 
solder ;  V)ut  the  better  way  is  to  attach  them  to  each  other  tem- 
porarily, with  adhesive  wax,  in  the  relation  they  occupy  on  the 
model,  and  then  remove  them  carefully  and  imbed  the  clasps 
and  i)alatal  face  of  the  plate  in  a  mixture  of  nearly  equal 
parts  of  plaster,  sand,  and  asbestos.  Before  uniting  the  two 
•pieces  on  the  model  with  wax,  however,  the  ends  of  the  clasps 
should  be  straightened  out  or  spread  apart,  in  order  that  they 
may  part  readily  from  the  plaster  teeth,  without,  in  any  de- 
gree, changing  their  exact  relation  to  the  plate ;  in  doing 
which,  it  should  be  observed  that  all  parts  of  the  clasps  which 
are  to  be  united  to  the  })late  should  remain  in  close  contact 
with  the  plaster  teeth.  After  the  plaster  mixture,  in  which 
the  plate   and  clasps    are   imbedded,  has  become  sufficiently 


218  MECHANICAL   DENTISTRY. 

hard,  the  portions  of  wax  which  temporarily  united  the  latter 
should  be  removed,  and  the  surfaces  of  the  clasps  and  plate, 
where  they  unite  with  each  other,  smeared  with  borax  ground 
in  water  to  the  consistence  of  cream ;  small  pieces  of  solder 
are  then  placed  along  the  lines  of  contact,  the  investient  heated 
in  the  furnace  until  the  plate  acquires  a  full  red  heat,  when  it 
is  removed,  placed  upon  a  suitable  holder,  and  the  solder  fused 
with  the  blowpipe. 

Whenever  the  form  and  inclination  of  the  teeth  to  be  clasped 
are  not  fairly  represented  on  the  model,  owing  to  dragging  or 
displacement  of  the  wax  in  withdrawing  the  impression,  the 
difficulties  of  securing  a  proper  relative  adjustment  of  the  sev- 
eral parts  of  the  appliance  will  be  increased  ;  but  either  of  the 
following  methods,  if  carefully  and  accurately  manipulated, 
will  secure  accurate  results. 

1.  Gutta-percha  may  be  substituted  for  wax  when  taking 
an  impression  with  the  plate  in  the  mouth.  With  the  proper 
use  of  this  material,  the  exact  form  and  inclination  of  the 
teeth  will  be  preserved ;  and  when  employed,  it  should  be 
filled  in  Avith  plaster  for  the  model  immediately  after  removing 
it  from  the  mouth.  The  subsequent  steps  in  the  operation  are 
precisely  similar  to  those  described  when  wax  is  used. 

2.  Another  method  is  to  adjust  the  clasps  and  plate  to  the 
parts  in  the  mouth,  attach  them  temporarily  in  their  proper 
relation,  and  remove,  invest,  and  solder  in  the  usual  way. 
This  may  be  accomplished  in  the  following  manner :  First, 
spread  apart  the  ends  of  the  clasp  somewhat  to  permit  it  to  be 
easily  removed  from  the  tooth ;  place  this  upon  the  tooth  in 
the  mouth  to  be  clasped  ;  then  adjust  the  plate  in  the  mouth, 
and  attacli  the  two  to  each  other  by  pressing  a  piece  of  stiif, 
adhesive  wax  in  against  the  clasp  and  plate  where  they  unite ; 
harden  the  wax  by  placing  against  it,  for  a  few  minutes,  the 
end  of  a  napkin  moist  with  cold  water ;  then  remove  the  plate 
and  clasp  carefully  from  the  mouth,  and  invest  and  solder  as 
before.  The  plate,  with  one  clasp  permanently  attached,  is 
now  placed  back  in  the  mouth,  and  the  second  clasp  adjusted 
to  the  tooth  on  the  opposite  side  in  the  manner  before  alluded 


CLASPS.  219 

to;  this  is  tlien  temporarily  fastened  to  the  plate  and  other- 
wise treated  in  like  manner  as  the  one  first  described.  If  the 
teeth  to  be  clasped  are  favorably  formed  and  regularly  ar- 
ranged in  the  arch,  both  clasps  may,  at  the  same  time,  be  tem- 
porarily attached  to  the  plate  in  the  fii*st  instance ;  if  not,  it 
will  be  impracticable  to  remove  them  from  the  teeth  without 
disturbing  the  wax  and  changing  their  relation  to  the  base 
and  the  teeth  clasped.  The  additional  labor  and  consumption 
of  time  incident  to  a  separate  attachment  of  the  clasps,  Avill,  in 
proportion  as  they  secure  better  results,  amply  reward  the  op- 
erator for  his  painstaking. 

Plaster  is  sometimes  substituted  for  wax  in  this  process ;  in 
which  case  it  is  introduced  into  the  mouth  on  a  small  piece  of 
wax  or  sheet  lead  and  pressed  gently  against  the  uniting  por- 
tions of  the  plate  and  clasp,  and  allowed  to  remain  until  suf- 
ficiently hard.  Any  superfluous  portions  around  the  tooth 
that  may  hinder  the  easy  removal  of  the  clasp  should  now  be 
cut  away,  when  the  pieces  so  attached  to  each  other  are  re- 
moved from  the  mouth.  A  separation  of  the  plaster  from  the 
clasp  or  plate,  or  both,  may  occur  when  removing  the  latter ; 
in  this  case  the  several  parts  may  be  readily  and  accurately 
adjusted  to  each  other  again  in  their  exact  relation  when  out 
of  the  mouth ;  as  the  latter  will  be  plainly  indicated  by  the 
impression  made  by  the  plate  and  clasp  in  the  plaster.  Being 
readjusted,  they  may  be  further  secured  by  sticking  them  to- 
gether with  a  little  softened  wax,  when  they  are  invested,  the 
temporary  fastenings  of  plaster  removed,  and  the  pieces  united 
l)y  soldering.  The  use  of  plaster  in  these  cases  is  due  to  Dr. 
Lester  Xoble,  and  unquestionably  possesses  many  advantages 
over  wax  for  the  purpose,  as  the  latter  is  liable  even  with  the 
most  skilful  manipulation,  to  become  displaced  in  removing  it 
from  the  mouth;  and  this  change,  when  it  occurs,  not  being 
indicated  by  inspection  of  the  m  ax,  is  incapable  of  timely  cor- 
rection. 

3.  Still  another  method  is  that  contrived  by  Dr.  Fogle  and 
describc<J  Ijy  Dr.  Cusihman  in  the  tenth  volume  of  the  American 
Journal  of  Denial  Science.     It  consists  in  securing  the  proper 


^20  MECHANICAL   DENTISTEY. 

relation  of  the  clasps  to  the  teeth  in  the  mouth  by  the  use,  in 
the  first  instance,  of  what  are  termed  "  temporary  fastenings." 
The  plate  and  clasps  are  first  applied  to  the  model,  and  are  then 
connected  by  a  narrow  strip  of  plate  or  piece  of  wire  bent  in 
the  form  of  a  bow,  the  concavity  facing  the  model,  one  end  of 
which  is  soldered  to  the  palatal  side  of  the  clasp,  and  the  other 
to  a  contiguous  point  upon  the  plate.  The  pieces  thus  tempo- 
rarily united  are  removed  from  the  model  and  adjusted  to  the 
parts  in  the  mouth.  If  the  position  of  the  clasps  is  found  in 
any  respect  faulty,  they  can  be  easily  and  accurately  adapted 
to  the  walls  of  the  teeth  by  bending  or  twisting  the  connecting 
strip  in  any  desired  direction  with  pliers  or  other  instruments 
suitable  for  the  purpose.  This  accomplished,  the  plate  and 
clasps  are  removed,  and  the  operation  of  permanently  uniting 
the  clasps  to  the  plate  performed  in  the  usual  manner. 


CYLINDEES    OF    WOOD    ATTACHED    TO   TUBED   PLATES.       221 


CHAPTER  YII. 

Partial  Dentures  supported  in  the  Mouth  by  means 
OF  Cylinders  of  Wood  attached  to  Tubed  Plates. 

The  following  description  of  a  method  of  supporting  partial 
sets  of  teeth  in  the  mouth  by  means  of  wood  cylinders  attached 
to  the  plate  is  copied  from  an  article  contributed  by  Dr.  W.  M. 
Hunter  to  the  fourth  volume  of  the  American  Journal  of  Dental 
Science.  The  same  principle  has  long  been  made  available  in 
Europe  in  attaching  artificial  substitutes  constructed  of  the  hip- 
popotamus ivory,  but  the  credit  of  its  application  to  metallic 
plates  is  alike  due  to  Drs.  Hunter  and  Charles  Stokes  of  London. 

."After  swaging,  the  plate,  as  usual,  is  tried  in  the  mouth, 
and  an  accurate  impression  of  the  teeth  to  be  used  is  taken  over 
the  plate,  as  recommended  by  Dr.  Arthur,  in  the  American 
Journal,  which  will  show  the  exact  position  of  the  tooth  in  its 
relation  to  the  plate;  after  which  the  edge  of  the  plate  sur- 
rounding the  teeth  to  be  made  use  of,  should  be  doubled  or 
wired,  wlien  the  tubes  may  be  soldered  at  their  proper  points, 
taking  care  never  to  apply  pressure  to  one  side  of  a  tooth  with- 
out some  means  of  counteracting  the  effect ;  the  means  being 
either  a  .sufficient  number  of  natural  teeth  contiguous  to  the  tooth 
to  be  used,  a  counter  tube,  an  arm  of  metal,  or  an  artificial 
tooth,  depending  entirely  upon  the  nature  of  the  case. 

"  At  times,  it  is  well  to  tube  but  one  side  of  the  plate  and 
clasp  the  other ;  in  cases  where  the  crown  of  the  tooth  is  much 
larger  than  the  neck,  a  beautiful  application  may  be  thus  made. 

"  'J'lie  tubes  should  be  from  one-eighth  of  an  inch  to  one 
line  in  diameter,  and  should  be  filled  with  whiting  before  ap- 
plying heat,  to  j)revent  them  from  filling  with  solder  at  the  time 
of  soldering  to  the  plate.  They  should  be  placed  upon  the 
plate  so  carefully,  that  the  mouth  of  the  tube  Avill  come  in  con- 


222  MECHANICAL    DENTISTRY. 

tact  with  the  natural  tooth,  as  it  is  desirable  to  have  the  wood 
protrude  but  very  slightly  beyond  the  orifice. 

"  When  it  can  be  properly  done,  the  tubes  are  soldered  at 
the  same  time  the  teeth  are,  as  it  saves  much  trouble  in  fitting ; 
it  cannot,  however,  be  very  well  done  where  it  is  designed  to 
fit  a  tooth  over  a  tube,  but  can  very  readily  be  done  where 
the  tooth  is  designed  to  fill  the  angle  caused  by  the  meeting  of 
the  stay  and  plate,  in  the  incisors  and  canine  teeth,  and  where 
a  canine  is  used  for  a  bicuspid,  building  over  the  tube  with 
metal  to  form  the  inner  cusp." 

The  accompanying  cuts  show  clearly  the  form  and  applica- 
tion of  the  tubes  referred  to.  In  Fig.  88,  showing  on  one 
side  but  a  single  tube,  the  counter-force  is  obtained  by  the 


artificial  tooth  which  rests  against  the  anterior  face  of  the  one 
to  which  the  wood  cylinder  is  applied.  Fig.  89  exhibits 
tubes  arranged  on  one  side,  and  a  clasp  on  the  other;  and 
shows  the  substitution  of  a  canine  for  a  bicuspid,  with  an 
inner  cusp  built  up  over  the  tube,  practically  converting  a 
cuspid  into  a  bicuspid  tooth. 

In  commenting  on  the  application  of  this  principle  to  partial 
sets  of  teeth,  Dr.  H.  remarks :  "  The  advantages  in  many  cases 
must  be  apparent  to  the  thinking  dentist,  but,  perhaps,  it 
might  not  be  amiss  to  enumerate  a  few. 

"  The  fixture  is  held  in  place  with  greater  firmness  than  by 
means  of  clasps. 

"  In  some  instances  where  I  have  used  clasps,  I  have  also 
used  the  tube  in  combination,  to  give  stability  for  masticating 
purposes. 


CYLIXDEES  OF  "WOOD  ATTACHED  TO  TUBED  PLATES.   223 

"The  injury  to  the  natural  teeth  must  be  much  less,  owing 
to  the  smaller  amount  of  surface  in  contact. 

"  If  decay  should  take  place,  it  would  require  but  an  ordi- 
nary filling  to  restore  the  tooth. 

"  It  prevents  that  peculiarly  disagreeable  sensation  experi- 
enced, particularly  in  fruit  season,  upon  removing  and  replac- 
ing artificial  teeth. 

"  After  having  tested  it  for  more  than  a  year,  I  am  satisfied 
that  it  greatly  lessens  the  chances  of  decay  in  those  cases  where 
it  can  be  applied,  and  I  have  removed  the  clasps  in  some  old 
cases  with  great  satisfaction  to  my  patients." 


224  MECHANICAL   DENTISTEY. 


CHAPTER  yill. 

Partial  Dentuees  supported  in  the  Mouth  by  Piv- 
oting THE  Plate  to  the  Roots  of  the  Natural 
Teeth. 

A  limited  number  of  teeth  may  be  mounted  on  a  plate 
pivoted  to  the  roots  of  two  or  more  of  the  front  teeth ;  and 
provided  the  latter  are  firm,  well  formed,  and  in  a  healthy 
condition  at  the  time  of  the  operation,  an  appliance  so  adjusted 
may  be  worn  by  the  patient  with  comparative  comfort  and 
efficiency  for  from  five  to  eight  years. 

Ordinarily,  the  roots  of  the  cuspidati  afford  the  most  secure 
means  of  attachment,  and  will  furnish  adequate  support  to  a 

Fig.  90.  Fig.  91. 


substitute  supplying  the  loss  of  a  part  or  all  of  the  teeth 
anterior  to  the  bicuspids  (Fig.  90),  and,  in  some  cases,  one  or 
two  of  the  latter  on  each  side.  The  roots  of  the  incisors,  also, 
may  be  used,  or  one  of  the  latter  and  a  cuspidatus.  In  some 
cases  the  plate  may  be  secured  in  the  mouth  by  pivoting  to  a 
root  on  one  side,  or  in  front,  and  clasping  to  a  tooth  on  the 
opposite  side  (Fig.  91),  provided  the  crown  of  the  latter  and 
the  pivot  root  stand  nearly  or  quite  parallel  with  each  other, 
as  any  considerable  deviation  from  this  relation  will  render  it 
difficult  or  impossible  to  apply  and  remove  the  substitute. 
The  roots  of  the  teeth  to  be  used  as  a  means  of  support 


PIVOTING   TO   THE    ROOTS    OF   THE    NATURAL   TEETH.       225 

should  be  prepared  in  the  manner  described  under  the  head  of 
"  Pivoting  Artificial  Crowns,"  In  all  cases,  the  enlarged  canal 
of  the  root  should  be  jirovided  with  a  gold  tube,  as  this 
method  is  the  only  one  which  will  protect  the  root  from  the 
mechanical  action  of  the  pivot,  or  permit  a  ready  or  frequent 
removal  of  the  appliance  for  the  purpose  of  cleansing  it  and 
the  parts  associated  with  it  in  the  mouth. 

The  roots  being  prepared  in  the  manner  indicated,  an  im- 
pression of  the  mouth  is  taken,  and  with  a  die  and  counter 
obtained  from  a  plaster  model  of  the  ])arts,  a  plate  of  the 
required  form  is  swaged  covering  the  filed  extremities  of  the 
roots  to  be  pivoted,  and  extending  anteriorly  very  nearly  or 
quite  to  the  free  margins  of  the  gum  in  front.  The  plate,  at 
those  points  corresponding  with  the  openings  into  the  roots, 
is  then  perforated  and  enlarged  sufficiently  to  admit  of  the 
passage  of  the  metallic  pivots;  tire  form  and  position  of  the 
orifices  in  the  roots  being  transferred  to  the  metallic  die,  the 
corresponding  de])ressions  in  the  plate  at  these  points,  w'hen 
the  latter  is  swaged,  will  serve  as  a  sufficient  guide  in  perfo- 
rating the  plate  for  the  pivots.  The  plate  is  now  applied  to 
the  mouth,  and  the  metallic  pivot,  one-half  longer  than  that 
ultimately  required  and  formed  to  fit  the  tube  accurately  but 
not  tigiitly,  is  passed  through  the  opening  in  the  plate  and 
pressed  to  the  bottom  of  the  tube,  leaving  the  surplus  portion 
of  the  pivot  projecting  on  the  lingual  side  of  the  plate.  The 
plate  and  pivot  are  now  secured  in  this  precise  relatixDu  by  im- 
bedding the  projecting  portion  of  the  latter  and  the  parts  of 
the  plate  immediately  surrounding  it,  in  a  batter  of  plaster. 
When  the  plaster  has  hardened,  the  plate  and  pivot,  with  the 
plaster  attached,  are  removed  in  their  undisturbed  relation 
from  the  mouth.  To  ]>rcscrve  the  several  pieces  in  situ  more 
perfectly,  the  projecting  end  of  the  pivot  may  be  flexed,  or  a 
head  formed  on  it  with  the  file  before  applying  the  plaster;  the 
pivot  thus  secured  will  bring  all  f)arts  together  if  traction  is 
made  on  the  plate  in  the  act  of  withdrawing  the  pivot. 

The  plate  being  removed  from  the  mouth,  its  palatal  por- 
tion is  imbedded  in  the  plaster  mixture,  and  when  the  latter 

15 


226  MECHANICAL    DENTISTEY. 

is  hard,  the  plaster  is  removed  from  around  the  pivot  on  the 
opposite  side  of  the  plate,  and  the  pivot  permanently  united 
by  flowing  solder  at  its  point  of  contact  with  the  plate.  The 
redundant  portion  of  the  pivot  on  the  lingual  side  of  the  base 
is  then  cut  and  filed  away  even  with  the  surface  of  the  latter. 
If  the  manipulations  have  been  accurately  conducted,  the  plate 
and  pivot,  on  being  reapplied  to  the  parts  in  the  mouth,  will 
be  found  to  adapt  themselves  perfectly  to  the  palatal  arch  and 
roots. 

It  is  better,  unless  the  roots  to  be  pivoted  stand  nearly  or 
quite  parallel,  to  adjust  and  solder  but  a  single  pivot  at  a 
time,  as  but  a  very  slight  variation  in  the  direction  of  the 
roots  would  render  the  withdrawal  of  both  pivots  at  the  same 
time  difficult  or  impracticable  without  more  or  less  change  of 
relation.  The  same  may  be  remarked  of  those  cases  where  a 
clasp  is  used  in  conjunction  with  the  pivot. 

The  most  efficient  method  of  rendering  the  appliance  sta- 
tionary when  applied  to  the  roots,  and  at  the  same  time  of 
enabling  the  patient  to  readily  apply  and  remove  it  at  will,  is 
that  recommended  by  Dr.  Dwindle,  and  which  consists  in 
splitting  the  pivot  with  a  fine  saw,  and  spreading  the  sections 
apart  somewhat,  thus  giving  them  an  increased  lateral  bearing. 

Gold  used  for  pivots  in  these  cases  should  be  alloyed  with 
platinum,  as  that  ordinarily  employed  for  plate  is  too  inelastic 
for  the  purpose. 


ATMOSPHERIC    PRESSURE. 


227 


CHAPTER  IX. 

Partial  Dentures  Supported  in  the  Mouth  by 
Atmospheric  Pressure. 


The  method  of  attaching  partial  sets  of  teeth  to  the  superior 
jaw  by  means  of  atmospheric  pressure,  is  much  more  generally 
practiced  now  than  formerly,  and  whenever  the  condition  of 
the  soft  parts  of  the  mouth,  the  general  configuration  of  tlie 
palatal  arcli,  and  the  antagonism  or  occlusion  of  the  artificial 
witli  the  natural  teeth  favor  its  adoption,  there  are  good  and 
sufficient  reasons  why  it  should  be  preferred,  in  all  practicable 
cases,  to  either  of  the  other  methods  heretofore  described. 

Modifications  in  the  Form  of  the  Base. — If  vacuities  exist  at 
various  points  on  the  ridge,  the  plate  on  which  the  teeth  of  re- 
placement are  mounted,  should  be  ample  in  its  dimensions, 
covering    nearly  or    quite  all  Fig.  92. 

of  the  hard  palate.  The  gen- 
eral form  of  the  base  wher- 
several  teeth  scattered  through- 
out the  arch  are  required,  is 
shown  in  Fig.  92.  In  most 
cases,  whether  but  one  or  a 
greater  number  of  teeth  are  to 
be  replaced,  increased  adhe- 
rence and  stability  of  the  sub- 
stitute will  be  better  secured 
by  permitting  the  plate  to  cover  the  larger  portion  of  the  roof 
of  the  mouth ;  though,  in  cases  that  present  the  best  form  of 
the  vault,  a  diminished  surface  may  be  given  to  the  base  with 
cfjually  satisfactory  results.  In  the  substitution  of  a  single 
incisor,  for  example,  it  will  frequently  be  sufficient  to  employ 
a  very  small  plate,  covering  only  a  part  of  the  anterior  sloping 


228 


MECHANICAL    DENTISTRY. 


wall  of  the  palate.  (Fig.  93.)  lu  the  latter  case,  the  plate 
used  may  be  very  thin,  say  No.  30  of  the  gauge  ;  it  will  thus 
impede  the  movements  of  the  tongue  less,  and  may  be  swaged 
more  accurately  to  the  parts.  If  constructed  with  an  air-cham- 
ber, the  latter  should  be  quite  shallow. 

A  somewhat  anomalous  form  of  atmospheric  pressure  plate 
employed  in  the  substitution  of  one  or  two  bicuspid  teeth  on 
each  side  is  described  by  Professor  Taft,*  the  design  of  which 


Fig.  94. 


is  to  secure,  in  such  cases,  increased  stability  of  the  substitute, 
while  much  of  the  palatal  arch  is  left  uncovered.  It  consists, 
as  will  be  seen  by  reference  to  Fig.  94,  of  two  lateral  cavity 
plates  accurately  adjusted  to  the  sloping  walls  of  the  palate  on 
each  side,  immediately  adjoining  and  partly  occupying  the 
spaces  to  be  supplied.  These  lateral  plates  may  be  made  as 
large  as  a  dime,  or  somewhat  larger,  and  of  an  elliptical  shape, 
if  both  bicuspids  on  the  same  side  are  to  be  replaced,  and  are 
connected  with  each  other  by  a  narrow  band  of  gold  plate,  two 
lines  or  more  in  width,  having  an  anterior  curvature,  and 
resting  on  the  front  wall  of  the  palate,  two  or  three  lines  behind 
the  anterior  teeth.  The  entire  appliance  may  be  constructed 
from  a  single  piece  of  gold  plate  swaged  accurately  to  the 
parts ;  or  the  lateral  plates  and  connecting  band  may  be  sepa- 
rately swaged  and  secured  in  their  proper  relation  to  each 
other  in  the  mouth  with  wax  or  plaster,  when  they  are  care- 


*  Dental  Register  of  the  West,  vol.  xiii,  p.  112. 


ATMOSPHERIC   PEESSUEE.  229 

fullv  removed,  invested,  and  soldered  together;  it  should  then 
be  re-swaged  to  correct  any  change  of  relation  that  may  have 
happened  during  the  concluding  manipulations.  The  liability 
of  the  plate  to  ride  upon  the  central  and  raised  portion  of  the 
palate,  when  pressure  is  made  upon  one  side,  throwing  the 
plate  off  from  the  ridge  on  the  other,  as  in  the  case  of  a  base 
extending  across  the  arch,  is  in  a  great  degree  obviated  by  the 
method  just  described. 

Manner  of  Forming  an  Air-chamber. — Atmospheric  pres- 
sure plates  for  partial  cases  are  usually  constructed  with  a 
central  air-chamber;  in  which  case,  the  part  of  the  model 
representing  the  chamber  may  be  formed  in  either  of  the  ways 
mentioned  in  the.  chapter  on  "  Plaster  Models."  The  model 
prepared,  the  form  of  the  plate  to  be  used  is  first  indicated 
thereon,  and  from  this  a  pattern  in  sheet  lead  is  obtained, 
which  is  placed  on  the  plate  of  gold  or  other  metal,  and  its 
outlines  traced  with  a  pointed  instrument;  the  redundant  por- 
tions are  then  cut  away  with  plate-shears  and  forceps.  The 
plate  is  now  placed  on  the  die,  and  brought  as  nearly  as  possi- 
ble into  adaptation  to  the  latter  with  the  mallet  and  pliers ;  it 
is  tlien  interposed  between  the  die  and  counter,  and  swaged 
until  it  conforms  perfectly  to  the  face  of  the  former ;  annealing 
the  plate  frequently  to  render  it  more  pliant  and  manageable 
under  the  hammer.  Unless  the  plate  used  is  purer  and  thin- 
ner than  is  generally  employed,  or  than  is  consistent  with  the 
required  strength,  it  will  fail  to  be  forced  perfectly  into  the 
groove  around  the  chamber  by  the  process  of  swaging  alone  ; 
a  more  definite  border,  ho\v'ever,  may  be  formed  by  forcing 
the  j)late  in  at  this  place  with  a  small,  smooth-faced  stamp, 
shaped  to  the  angle  of  the  groove,  passing  round  the  chamber 
and  carefully  forcing  the  plate  in  with  the  stamp  and  a  small 
hammer  or  mallet  until  a  somewhat  sharp  and  abru])t  angle  is 
obtained  to  the  palatal  edge  of  the  chamber.  After  the  cham- 
ber is  as  perfectly  formed  as  possible  in  this  way,  the  plate 
should  l>e  well  annealed  and  again  swaged  to  correct  any  par- 
tial deformity  occasioned  by  stamping  the  chamber. 

A  still  more  perfectly  defined  angle  may  be  given  to  the 


230  MECHANICAL    DENTISTRY. 

borders  of  the  chamber  in  the  following  manner  :  After  SM^ao;- 
ing  the  plate  sufficiently  to  indicate  the  exact  position  and 
form  of  the  chamber,  the  portion  forming  the  latter  should  be 
separated  from  the  main  plate  by  completely  dividing  it  with 
a  small,  sharp,  chisel-shaped  instrument,  cutting  on  a  line  with 
the  groove  around  the  chamber  until  the  latter  is  entirely  sepa- 
rated. The  cut  portion  of  the  main  plate  is  then  trimmed 
evenly  with  a  file,  being  -careful  not  to  enlarge  the  opening 
more  than  is  required  to  remove  the  irregularities  of  the  edge 
formed  in  cutting.  The  plate,  with  its  central  portion  removed, 
is  then  placed  upon  the  die,  when  a  separate  piece  of  gold  cut 
to  the  general  form  of  a  chamber,  but  somewhat  larger  than 
the  opening  in  the  main  plate,  is  adjusted  over  the  chamber, 
and  struck  up  with  the  plate  until  the  overlapping  portions  of 
the  central  piece  are  forced  down  upon  the  plate  around  the 
margins  of  the  chamber.  It  is  not,  however,  always  necessary 
to  employ  a  separate  piece  of  gold  for  the  chamber,  as  the  cen- 
tral portion  cut  from  the  plate  in  the  first  instance  may  be  suf- 
ficiently enlarged  for  the  purpose.  This  is  accomplished  by 
first  flattening  out  the  detached  portion,  annealing  it,  and  then 
passing  successive  portions  of  its  edges  a  sixteenth  of  an  inch 
or  more  between  the  rollers,  the  latter  being  sufficiently  ap- 
proximated to  produce  a  perceptible  thinning  of  the  margins. 
When  the  entire  border  of  the  chamber  piece  has  been  thus 
attenuated  and  extended,  it  will  be  found  so  much  enlarged 
that  when  adjusted  to  the  die  and  swaged  in  connection  with 
the  main  plate,  its  borders  will  overlap  and  rest  upon  the  mar- 
gins of  the  opening  in  the  base,  as  in  the  other  case. 

The  portions  of  the  plate  and  cut  chamber  lying  in  contact 
are  now  coated  with  borax  and  pieces  of  solder  placed  along 
the  line  of  union  on  the  lingual  side  of  the  plate,  when  the  two 
pieces,  being  transferred  to  a  bed  of  charcoal,  are  permanently 
united  by  flowing  the  solder  with  a  blowpipe.  Sufficient  heat 
should  be  applied  to  induce  an  extension  of  the  solder  between 
the  two  portions  of  plate,  filling  up  completely  the  gap  between 
them  to  the  edge  of  the  orifice  in  the  main  plate,  forming,  at 
this  point,  a  square  and  well-defined  angle  to  the  margins  of 
the  chamber. 


SELECTIXG    AND    AERAXGIXG   THE   TEETH.  231 


CHAPTER  X. 

Method  of  Obtaining  an  Antagonizing  Model  for 
Partial  Dentures;  Selecting,  Arranging,  and 
Antagonizing  the  Teeth  ;  Investing,  Adjusting 
Stays,  Soldering,  Etc. 

Haying  constructed  the  plate  or  base  to  be  used  as  a  sup- 
port for  partial  sets  of  teeth  in  either  of  the  ways  described  in 
the  preceding  chapter,  it  will  be  necessary,  before  arranging 
the  teeth  on  the  plate,  to  secure  an  accurate  representation  of 
all  the  remaining  natural  teeth  of  both  jaws  in  plaster,  pre- 
serving accurately  the  relation  which  these  organs  bear  to 
each  other  in  the  mouth.  This  is  effected  by  what  is  called 
an  antagonizing  model,  and  may  be  secured  in  the  following 
manner : 

.  A  roll  or  strip  of  adhesive  wax  is  first  attached  to  the  lin- 
gual border  of  the  plate,  and  its  adhesion  secured  by  holding 
the  opposite  side  of  the  plate  for  a  moment  over  the  flame  of  a 
spirit-lamp.  The  wax  used  for  articulating  purposes  should 
be  harder  and  more  tenacious  than  plain  beeswax,  and  may  be 
compounded  from  the  following  formula: 

Beeswax, 1  pound 

Guru  inastich, 2  ounces 

Spanish  wliiting, 1  ounce 

The  wax  is  first  melted  in  a  shallow  vessel,  and  the  mastich, 
finely  pulverized,  gradually  added,  and  then  the  whiting,  stir- 
ring constantly  until  thoroughly  incorporated.  The  rim  of  wax 
being  arranged  on  the  plate,  all  superfluous  portions  over- 
hanging the  margins  occupied  by  the  remaining  teeth  are  cut 
away ;  the  plate  may  then  be  placed  on  the  model  and  the 
wax  again  trimmed,  leaving  it  somewhat  fuller  than  the  outer 


232  MECHANICAL    DENTISTRY. 

circle  of  the  teeth,  and  from  one  to  three  lines  longer  than  those 
immediately  adjoining  the  spaces.  The  plate,  with  the  wax 
attached,  is  then  placed  in  its  proper  position  in  the  mouth, 
and  the  patient  instructed  to  close  the  jaws  naturally  until  the 
remaining;  teeth  meet :  one-third  or  more  of  the  crowais  of  the 
opposing  teeth  opposite  the  spaces  will  thus  be  imbedded  in 
the  wax.  A  still  fuller  impression  of  the  opposing  teeth  may 
be  obtained,  if  desired,  by  pressing  the  edges  of  the  wax  down 
upon  the  crowns  with  the  finger.  If  a  series  of  anterior 
teeth  are  to  be  replaced,  the  mesial  line  of  the  mouth  in  front 
should  be  indicated  upon  the  wax  by  drawing  a  line  vertically 
across  the  latter  to  serve  as  a  guide  in  the  arrangement  of  the 


Fig.  95. 


central  incisors  and  adjoining  teeth.  The  plate  and  wax  are 
then  carefully  removed  from  the  mouth  and  again  placed  upon 
the  plaster  model,  the  latter  having  been  previously  obtained 
from  an  impression  of  the  parts  with  the  plate  in  the  mouth. 
The  model  is  then  placed  on  a  slip  of  paper  with  the  plate  and 
wax  upward,  and  the  heel  of  the  model  extended  from  one  to 
two  inches  posteriorly  to  form  an  articulating  surface  for  the 
remaining  portion  of  the  antagonizing  model.  The  added 
portion  of  plaster  may  be  confined  by  a  narrow  strip  of  wax 
or  sheet-lead  extending  back  upon  each  side  of  the  model,  into 
which  a  batter  of  plaster  is  poured  to   the  depth  of  half  or 


SELECTING    AND    ARRANGING   THE   TEETH. 


233 


thrcc-fonrths  of  an  inch.  When  hard,  the  edges  and  upper 
surface  of  the  added  phister  should  be  trimmed  smooth,  and  a 
crucial  groove,  or  two  or  three  conicaI-shai)ed  holes,  cut  in  the 
surface  of  tiie  latter  to  secure  a  fixed  and  definite  relation  of 
the  two  parts  of  the  model.  The  articulating  surface  is  then 
varnished  and  oiled  to  prevent  the  next  portion  of  })iaster  from 
adhering  ;  the  imprints  of  the  teeth  in  the  wax  are  also  oiled. 
This  portion  of  the  antagonizing  model,  with  the  plate  and 
wax  attached,  is  exhibited  in  Fig.  95.  The  open  sj)ace  look- 
ing into  the  ])alatal  vault  should  be  closed  with  a  sheet  of 
softened  wax  to  prevent  the  next  portion  of  plaster  from  flow- 
ing into  the  cavity  underneath.  A  batter  of  plaster  is  now 
poured  carefully  upon  the  exposed  surface  of  the  wax,  filling 
the  imprints  of  the  teeth  perfectly,  and  extending  back  upon 

Fig.  96. 


the  heel  of  the  model  until  it  acquires  a  depth  of  half  an  inch 
or  more.  When  sufficiently  hard,  the  two  sections  of  the 
model  are  sejjarated,  superfluous  portions  triuinied  away, 
and  the  entire  surface  of  both  pieces  glazed  with  varnish.  The 
model  complete,  with  the  plate  in  place,  and  the  wax  (retained 
as  a  tem^jorary  support,  whilst  adju.sting  the  artificial  teeth) 
trimmed  as  required,  are  shown  in  Fig.  96,  and  if  the  manip- 
ulations have  been  accurate  this  simple  contrivance  will  ex- 
hibit all  the  parts  represented  in  plaster  in  precisely  the  same 
relative  position  which  they  occupy  in  the  mouth  when  the 
teeth  are  closed  upon  each  other.  It  will  be  seen,  by  reference 
to  Fig.  9o,  that  only  those  teeth  of  the  opposing  jaw  which 


234 


MECHANICAL   DEXTISTEY. 


Fig.  97. 


present  to  the  spaces,  are  represented  in  plaster,  as  these  are 
all  that  are  required  in  arranging  the  teeth  of  replacement. 

Selecting,  Arranging,  and  Antagonizing  the  Teeth. — The 
teeth  of  replacement  should  harmonize,  as  nearly  as  possible, 
in  size,  configuration,  and  color,  with  those  remaining  in  the 
mouth ;  and  when  selecting  teeth  for 
any  given  case,  the  operator  should  be 
provided  with  a  sufficient  number  of 
sample  teeth  to  meet  every  require- 
ment, by  comparison,  in  respect  to  the 
various  tints  or  delicate  shades  of  color 
characteristic  of  the  natural  teeth  and 
gums.  The  required  size  and  form  of 
the  artificial  teeth  may  be  determined 
with  tolerable  accuracy  by  a  compari- 
son with  those  on  the  plaster  model, 
but  the  form  or  figure  more  certainly 
by  a  careful  inspection  of  those  in  the 
mouth. 

A  greater  or  less  change  in  the  form 
of  porcelain  teeth  will  be  required,  in 
nearly  all  cases,  in  arranging  and  fit- 
ting them  to  the  vacuities  in  the  jaw ; 
and  this  is  more  particularly  so  in  those  cases  requiring  the 
use  of  gum  teeth.  This  alteration  of  form  is  effected  by  grind- 
ing away  portions  of  the  tooth  upon  an  emery  or  corundum 
wheel,  attached,  as  will  be  seen  in  Fig.  97,  to  a  foot-lathe.  If 
the  edentated  portions  of  the  ridge  have  suffered  but  little 
change  of  form  by  absorption,  as  w^here  the  teeth  have  been 
recently  extracted,  and  plate  teeth  (those  representing  only  the 
crowns  of  the  natural  organs)  are  used,  the  posterior  portions 
of  the  base  of  the  latter  resting  upon  the  margins  of  the  plate 
will  only  require  to  be  conformed  to  the  irregularities  on  the 
surface  of  the  base,  grinding  sufficiently  to  give  to  them  the 
proper  length  and  relative  position,  while  their  anterior  cer- 
vical portion  is  permitted  to  overlap  the  edge  of  the  plate  and 
rest  directly  upon  the  gum  in  front  on  a  line  with  the  adjoin- 


SELECTING    AXD    ARRANGING    THE   TEETH.  235 

ing  teeth.  AVhen,  however,  a  considerable  concavity  exists  in 
the  ridge  and  external  border,  and  single  gum  teeth  are  em- 
ployed to  restore  the  customary  fulness  and  contour  of  the 
parts,  the  gum  portion  of  the  tooth  should  be  ground  away  on 
its  posterior  face  sufficiently  to  restore  the  circle  of  the  gum  on 
the  external  border  of  the  alveolus,  and  from  the  base  of  the 
tooth  where  it  rests  upon  the  plate,  to  admit  of  a  proper  rela- 
tive position  of  the  artificial  crown ;  while  those  portions  of 
the  porcelain  gum  terminating  at,  and  adjoining  the  remain- 
ing teeth,  next  the  spaces,  should  be  formed  with  a  thin,  re- 
treating edge,  where  it  laps  upon  the  natural  gum,  giving  to 
the  parts,  when  the  substitute  is  adjusted  to  the  mouth,  the 
appearance  of  an  unbroken  denture  and  a  continuous  gum. 
When  the  space  to  be  supplied  requires  a  series  of  two  or 
more  single  gum  teeth,  the  latter  should  be  united  to  each 
other  with  the  greatest  care  and  exactness  by  grinding  the 
proximate  edges  of  the  gum  portions  until  the  coaptation  is 
such  as  to  render  the  seams  imperceptible  in  the  mouth.  In 
adjusting  the  porcelain  teeth  to  the  plate,  the  base  of  each 
tooth  should  be  ground  to  rest  as  directly  and  uniformly  on 
the  plate  as  possible;  for  if  thrown,  in  any  degree,  from  the 
plate,  the  whole  strain  in  mastication  will  come  upon  the 
platinum  rivets,  and,  in  a  comparatively  short  time,  the  latter 
will  either  be  entirely  worn  or  cut  off,  or  the  artificial  crown 
will  be  fractured  on  a  line  with  the  pins. 

In  antagonizing  partial  sets  of  teeth,  the  indications  pointed 
out  by  the  customary  closure  of  the  natural  organs  should 
be  followed  as  nearly  as  the  form  and  position  of  the  op- 
posing teeth  will  permit.  A  changed  or  abnormal  relation 
of  the  teeth  of  both  jaws,  however,  frequently  renders  it  diffi- 
cult tf»  effect  a  satisfactory  adjustment  of  the  teeth  of  replace- 
ment. If,  in  the  case  of  the  bicuspids,  for  example,  one  or 
more  teeth  in  the  under  jaw  project  into  a  vacuity  above  to  the 
extent  of  one-third  or  more  of  its  depth,  a  direct  closure  of  the 
substituted  organs  ujjon  these,  in  the  ordinary  manner,  would 
be  impracticable  without  a  corresponding  shortening  of  the 
porcelain   teeth,  enforcing,   in    such   cases,  an    inharmonious 


236  MECHANICAL    DENTISTRY. 

arrangement,  entirely  inconsistent  with  the  just  requirements 
of  the  case.  The  difficulty  cited,  Or  any  of  the  various  modi- 
fications of  it,  may  be  overcome  wholly  or  in  part  in  one  of 
two  or  three  ways.  If  the  teeth  encroaching  upon  the  opposite 
space  are  very  loose,  as  is  frequently  the  case  with  those  that 
have  become  elongated  from  the  long-continued  want  of  an 
adequate  opposing  force,  or  are  hopelessly  carious  or  otherwise 
diseased,  they  should  be  at  once  removed.  If  they  remain 
firm  and  sound,  and  stand  slightly  within  the  circle  of  the 
teeth  of  the  opposite  jaw,  or  if  they  have  somewhat  of  an  in- 
ward inclination  in  the  arch,  the  vacuity  opposite  may  be  filled 
with  non-masticating  teeth,  as  a  canine,  on  the  lingual  side  of 
which  an  antagonizing  cusp  of  gold  may  be  constructed, 
allowing  the  point  of  the  cuspid  to  lap  over  upon  the  labial 
face  of  the  encroaching  tooth  or  teeth ;  or  a  bicsupid,  manufac- 
tured for  the  purpose,  with  the  inner  cusp  near  the  base  of  the 
tooth,  may  be  used  instead.  Additional  room  may  be  pro- 
vided, in  such  cases,  for  the  overlapping  portion  by  filing 
away  from  a  corresponding  point  on  the  opposing  tooth.  If, 
however,  taking  the  most  impracticable  case,  the  intruding 
teeth  are  sound  and  firm,  and  stand  vertically  in  the  arch, 
closing  between  the  opposing  teeth  on  a  line  with,  or  some- 
what outside  of,  the  outer  circle  of  the  latter  (the  elongation 
of  such  teeth  being  rather  relative  than  absolute,  as  where  it 
results  from  a  mechanical  wearing  away  of  the  remaining  an- 
tagonizing teeth  and  a  corresponding  approximation  of  the 
jaws),  the  practitioner  will  be  compelled  either  to  submit  to  a 
mal-arrangement  of  the  teeth  of  replacement  by  grinding  away 
sufficiently  from  their  grinding  surfaces  to  permit  an  unob- 
structed closure  of  the  natural  organs,  or  decline  the  operation 
altogether. 

The  undue  projection  of  the  teeth  of  one  jaw  into  a  vacuity 
occurring  in  the  one  opposite  more  frequently  happens,  how- 
ever, in  connection  with  tlie  loss  of  the  superior  incisors.  In 
such  cases,  the  points  of  the  lower  incisors  very  frequently 
encroach  upon  the  circle  of  the  upper  teeth,  so  that  when  the 
artificial  teeth  are  arranged  above  in  correspondence  with  the 


SELECTING   AND    ARRANGING   THE   TEETH.  237 

circle  of  the  adjoining  teeth,  antl  the  jaws  are  approximated, 
the  points  of  the  inferior  teeth  will  strike  prematurely  either 
upon  the  cutting  edges  of  those  above  or  will  close  upon  their 
inner  surfaces, — impeding  thereby,  or  entirely  preventing,  the 
Qi^clusion  of  the  teeth  posterior  to  them.  For  such  cases  thin 
teeth  should  be  selected,  and  whenever  necessary  the  lower 
teeth  may  be  filed  away  sufficiently,  while  those  of  replacement 
should,  at  the  same  time,  be  arranged  as  prominently  as  the 
circle  will  admit  of.  If  these  expedients  fail,  and  a  sufficient 
number  of  teeth  posterior  to  the  incisors  require  to  be  substi- 
tuted in  connection  with  the  same  appliance,  it  will  be  better, 
in  cases  not  susceptible  of  satisfactory  correction  by  the  means 
already  suggested,  to  change  the  bite  by  substituting  an  entirely 
new  antagonism  with  the  artificial  teeth, — spreading  the  jaws 
sufficiently  apart  to  relieve  the  artificial  incisors  in  front. 

In  no  case,  except  that  last  described,  should  the  artificial 
teeth  come  in  contact  with  the  oi)posing  teeth  before  the  occlu- 
sion of  the  remaining  natural  organs  when  the  jaws  are  closed. 
The  contact  of  all  the  teeth  of  one  jaw,  artificial  and  natural, 
with  those  of  the  opposite,  should  either  be  simultaneous,  or 
the  natural  teeth  should  be  permitted  to  strike  first. 

In  view  of  the  difficulties  which  so  frequently  present  them- 
selves in  connection  with  the  arrangement  of  artificial  teeth  in 
partial  cases,  it  may  not  be  amiss  to  observe  that,  however 
essential  to  the  natural  and  agreeable  expression  of  the  indi- 
vidual an  exact  and  harmonious  arrangement  of  the  teeth  of 
replacement  may  be,  this  requirement  should,  in  some  degree, 
be  disregarded  whenever  the  necessities  of  the  patient,  in  re- 
spect to  the  comfort  and  utility  of  the  appliance  or  the  safety 
of  the  natural  organs,  demand  it ; — to  what  extent  appearances 
should  he  sacrificed  to  these  considerations  will  dejjend  upon 
the  ])eculiar  exigencies  of  the  case,  and  cannot,  therefore,  be 
specifically  stated.  On  the  other  hand,  it  may  be  observed  that, 
if  a  sufficient  numl)cr  of  the  natural  teeth  are  remaininjj  in 
both  jaws  to  enable  th(!  patient  to  ]X'rform,  with  tolerable  effi- 
ciency, the  act  of  mastication,  the  mere  utility  of  the  substitute 
in  regard  to  the  performance  of  this  function  may  l)e  partly  or 


238  MECHANICAL   DENTISTEY. 

wholly  disregarded  whenever  there  is  sufficient  reason  to  appre- 
hend that  the  substituted  organs  cannot  be  antagonized  with  a 
view  to  the  comminution  of  food  without  endangering  the  per- 
manency and  usefulness  of  the  appliance  by  necessitating  the 
application  of  forces  unfavorably  directed. 

Investing,  Adjusting  Stays,  Soldei^ing,  and  Finishing. — Hav- 
ing arranged  and  antagonized  the  teeth  as  accurately  as  possible 
on  the  plaster  model,  the  piece  should  be  placed  in  the  mouth 
to  detect  and  remedy  any  faultiness  that  may  be  found  to  exist 
either  in  the  adaptation,  position,  or  antagonism  of  the  artificial 
teeth.  It  is  then  removed  and  imbedded  in  a  mixture  of 
plaster,  sand,  and  asbestos,  in  the  proportion  of  about  two  parts 
of  the  former  and  one  part  each  of  the  latter.  The  body  of 
the  investient  may  be  surrounded  by  a  copper  or  sheet-iron 
band  to  prevent  the  plaster  from  breaking  away  whilst  adjust- 
ing the  stays  or  linings  to  the  teeth.  All  parts  of  the  plate 
and  teeth,  except  the  lingual  side  of  the  former  and  the  backs 
of  the  latter,  should  be  incased  in  plaster  to  the  depth  of  half 
an  inch  or  more,  and  when  the  latter  is  sufficiently  hard  all 
traces  of  wax  from  the  inside  should  be  carefully  detached 
with  suitable  instruments. 

The  piece  is  now  ready  for  the  adjustment  of  stays  or  back- 
ings, which,  when  permamently  united  by  soldering  to  the 
base  and  teeth,  are  designed  to  sustain  the  latter  in  position. 
These  supports  are  formed  from  plate  somewhat  thicker  than 
that  used  for  the  base;  a  heavier  and  stronger  stay  being 
necessary  when  they  are  not  united  laterally,  as  when  plate 
teeth  are  used.  If,  however,  single  gum  or  block  teeth  are 
employed,  and  the  stays  are  joined,  forming  a  continuous  band, 
plate  one-half  thicker  than  that  used  for  the  base  will,  ordi- 
narily, impart  adequate  security  to  the  attachment.  A  plain 
strip,  corresponding  in  width  with  the  tooth  to  be  lined,  is  cut, 
and  the  end  resting  on  the  main  plate  conformed  accurately 
with  the  file  to  the  irregularities  on  the  surface  of  the  latter, 
and  in  such  a  manner  as  to  permit  the  strip  to  take  the  direc- 
tion of  the  tooth.  The  general  form  of  the  stay  may,  in  the 
first  place,  be  obtained  by  cutting  a  strip  from  a  piece  of  gold 


SELECTING    AND   AERANGING   THE   TEETH. 


239 


with  a  pair  of  plate  forceps.  (Fig.  98.)  The  points  upon  the 
stay  to  be  pierced  for  the  admission  of  the  platinum  pins  may 
be  ascertained  by  coating  the  surface  of  the  former  with  wax 


Fig  98 


softened  in  the  flame  of  a  spirit-lamp,  and  pressing  it  first 
against  the  lower  pin,  the  point  of  which  will  be  indicated  by 
an  indentation  of  the  wax.     The  backing  is  then  perforated 


Fig.  99. 


at  this  point  with  a  plate  punch,  two  forms  of  which  are  ex- 
hibited in  Fig.  99,  one  armed  with  a  tongue,  which,  when  the 
plate  is  pierced,  forces  the  latter  from  the  punch.     The  strip 


240 


MECHANICAL    DENTISTRY. 


is  then  reapplied  to  the  upper  pin,  and  the  second  hole  obtained 
in  like  manner  as  the  first.  Instead  of  using-  wax,  the  ends  of 
the  rivets  may  be  stained  with  some  pigment,  which  will  show 
the  points  to  be  pierced  in  the  lining. 

Fig.  100  represents  an  ingeniously  contrived  instrumentj 
invented  by  Dr.  Samuel  Mallet,  and  designed  to  secure  an 
accurate  relation  of  the  two  holes.  After  straightening  the 
pins,  one  is  placed  in  the  hole  i,  at  the  head  of  the  punch, 
the  other  pin  pressing  out  the  movable  punch  e  (which  works 

Fig.  KO. 


by  the  spring  g),  until  it  slips  into  the  slot  h  ;  the  two  punches, 
/,  e,  then  make  the  holes  at  the  exact  distances  apart  to  receive 
the  pins. 

The  stay  should  be  adapted  accurately  to  the  face  of  the 
tooth;  it  is  then  cut  to  the  proper  length,  reaching  nearly  or 
quite  to  the  point  of  the  tooth,  and  then  shaped  with  a  file  to 
the  general  form  of  the  crown.  When  the  stays  are  to  be 
united  they  should  be  formed  with  a  shoulder  at  a  point  cor- 
responding with  the  neck  of  the  tooth,  and  the  proximate 
edges  below  united  closely  by  square  edges,  or  the  latter  may 
be  bevelled  and  made  to  lap  upon  each  other.  The  process  of 
soldering  will  be  greatly  facilitated  and  the  piece  will  be  more 
easily  and  artistically  finished,  by  securing,  in  the  first  in- 
stance, a  perfect  coaptation  of  all  the  parts  which  are  ulti- 
mately to  be  united.  The  sides  of  the  holes  in  the  stays  facing 
the  plate  should  now  be  enlarged  or  countersunk  with  a  spear- 
shaped  or  conical  burr  drill,  and  when  applied  to  the  teeth  the 


SELECTING   AND   ARRANGING   THE   TEETH.  241 

projecting  ends  of  the  platinum  pins  are  cut  off  even  with  the 
backings  and  then  split  and  spread  apart  with  a  small  chisel- 
shaped  instrument;  a  head  will  thus  be  formed  to  the  rivets 
when  solder  is  fused  upon  them,  and  which  will  prevent  them 
from  drawing  from  the  linings.  All  the  lines  of  union  between 
the  several  pieces  should  next  be  well  scraped,  exposing  a 
clean,  bright,  metallic  surface  to  the  solder ;  the  seams  are  then 
smeared  with  borax,  ground  or  rubbed  in  clean,  soft  water  to 
about  the  consistence  of  cream  ;*  after  which  small  j^ieces  of 
solder  are  placed  along  the  joints  and  over  the  points  of  the 
platinum  pins.  The  piece  thus  prepared  is  now  placed  in  the 
furnace  or  ordinary  fireplace,  in  order  to  heat  the  entire  mass 
throughout  preparatory  to  soldering.  The  fuel  most  proper 
for  this  purpose  is  charcoal,  either  alone  or  combined  with 
coke ;  the  latter  being  preferable  for  the  reason  that  charcoal 
alone  is  more  quickly  consumed,  and  burning  away  more 
rapidly  underneath,  the  piece  is  liable  to  drop  to  the  bottom  of 
the  furnace.  The  fuel  should  be  broken  into  small  pieces  and 
built  up  around  the  borders  of  the  investient,  in  order  that  all 
parts  of  the  latter  may  be  uniformly  heated.  The  heating 
process  should  be  conducted  gradually,  for  if  the  piece  to  be 
soldered  is  subjected  suddenly  to  a  high  heat,  the  plaster  will 
be  displaced  by  the  too  rapid  evolution  of  vapor,  and  the  in- 
tegrity of  the  porcelain  teeth  will  be  endangered.  The  piece 
may  be  allowed  to  remain  in  the  fire  until  the  plate  acquires  a 
visible  red  heat,  when  it  should  be  removed,  placed  ou  a  suit- 
able holder,  and  the  solder  fused  with  the  blowpipe.  A  broad, 
spreading  flame  should  first  be  thrown  over  the  entire  surface 
of  the  plate  and  border  of  the  plaster  until  the  temperature  of 
the  entire  mass  is  nearly  that  required  to  fuse  the  solder,  and 
which  is  indicated  by  the  latter  settling  and  contracting  upon 
itself;  the  flame  may  then  be  concentrated  upon  a  particular 
point,  as  at  the  heel  of  the  plate  on  one  side,  passing  round 

*  Slate  is  often  used  for  this  purpose,  but  is  unfit,  as  in  rubbing  the  borax, 
loosened  particles  of  the  former  become  mixed  with  the  latter  and  impede 
the  flow  of  the  solder,  and  becoming  entangled  render  it  unclean  and 
porous.     Ground  glass  or  a  porcelain  slab  is  the  best  for  the  purpose. 

16 


242 


MECHANICAL  DENTISTRY. 


from  tooth  to  tooth  until  all  parts  are  completely  united  and 
the  solder  is  well  and  uniformly  diffused. 

Having  united  the  teeth  to  the  plate,  the  piece  may  be 
allowed  to  cool  gradually,  or  it  may  be  plunged  after  the  lapse 
of  a  few  minutes  into  boiling  water  without  risk  of  injury  to 
the  teeth.  When  cool,  the  plaster  is  removed  and  the  plate 
placed  in  a  solution  of  equal  parts  of  sulphuric  acid  and  water, 
where  it  may  be  allowed  to  remain  until  the  discoloration  of 
the  plate  and  the  remains  of  the  vitrified  borax,  incident  to 
soldering,  are  removed ;  or  it  may  be  put  into  a  small  copper 
vessel,  partly  filled  with  the  same  solution  and  boiled  for  a  few 


Fig.  101. 


minutes.  After  removing  the  plate  from  the  acid,  it  should 
be  boiled  for  five  or  ten  minutes  in  a  solution  of  chloride  of 
soda  or  common  salt  and  water  to  remove  thoroughly  all  traces 
of  the  former.  Superfluous  portions  of  solder  are  now  to  be 
removed,  and  this  at  first  may  be  more  quickly  accomplished 
by  the  use  of  burrs  of  various  forms  and  sizes  attached  to  a 
lathe.  After  the  rougher  and  more  redundant  parts  are  thus 
cut  away,  any  remaining  irregularities  upon  the  surface  may 
be  further  reduced  with  properly  formed  files,  scrapers,  and 
cutting  instruments.  Flat  and  half-round  curved  files,  and 
scrapers  having  a  right  and  left  curvature  to  their  cutting 
edges,  and  chisel-shaped  cutting  instruments  for  paring  or 
chipping  away  (Fig.  101),  are  the  implements  usually  employed 
for  this  purpose,  and  with  which  a  comparatively  smooth  sur- 


SELECTING   AND   ARRANGING   THE   TEETH.  243 

face  may  be  obtained  ;  after  whicli,  the  filed  portions  should 
be  well  rubbed  with  Scotch  stone  until  all  traces  of  file-marks 
or  other  scratches  are  completely  removed.  With  a  rapidly 
revolving  brush  attached  to  a  foot-lathe,  the  final  polish  or 
lustre  may  be  imparted  by  the  use,  first,  of  Spanish  whiting, 
or  prepared  chalk,  and  then  rouge  mixed  with  water  or 
alcohol. 

The  following  method  of  finishing  plate-work  communi- 
cated by  Professor  J.  L.  Suesserott,*  embodies  some  practical 
suggestions  in  reference  to  this  process :  "  The  first  step  is  to 
procure  and  attach  to  the  lathe  a  three-  or  four-pronged  fork, 
or  a  screw  such  as  is  used  for  withdrawing  a  load  from  a  gun ; 
upon  this  a  good  smooth  cork  is  fixed,  and,  with  a  sharp  knife, 
turned  to  any  desired  shape.  The  cork  is  saturated  with  water 
as  well  as  it  can  be,  and  powdered  pumice  placed  upon  it.  If 
we  have  been  careful  to  remove  all  excess  of  solder  from  our 
work,  which  can  easily  be  done  by  a  burr  attached  to  the  lathe, 
we  can,  with  the  cork  and  pumice,  make  a  very  smooth  sur- 
face, and  this  can  be  still  more  perfectly  accomplished  by  sub- 
stituting a  very  finely  powdered  spar  for  the  pumice,  after  we 
have  removed  the  largest  scratches  with  tlie  latter.  By  con- 
tinuing the  cork  for  a  little  while  after  the  above-named  pow- 
ders have  been  used  oif,  we  avoid  the  use  of  the  Scotch  stone ; 
and  finally  we  dispense  with  the  burnisher,  by  taking  a  new 
cork  with  a  piece  of  chamois  or  buckskin  stretched  upon  it, 
and  going  over  the  plate  in  the  same  manner  as  before,  with 
the  lathe  revolving  very  rapidly. 

"  A  higher  color  can  be  given  to  the  plate  by  the  use  of  the 
burnisher  after  the  above  proceeding,  but  we  can  certainly  not 
produce  a  smoother  surface. 

"  Some  precaution  is  necessary  by  those  who  have  never 
used  the  lathe  in  finishing  the  j)late ;  in  the  first  place  the 
careless  use  of  the  burr,  in  removing  the  excess  of  solder,  might 
result  in  the  weakening  of  the  piece  by  removing  more  than 
neces.sary,  or,  what  would  .be  still  worse,  holes  might  be  cut 


*  Erroneously   aHcribod   in  tlie   fii-st    edition  to  Professor  T.    L.   Buck- 
ingham. 


244  MECHANICAL   DENTISTRY. 

entirely  through  the  plate.  Again,  in  polishing,  if  a  little 
care  is  not  taken,  the  fork  or  screw,  whichever  is  used,  may 
pass  through  the  cork,  and  before  the  operator  is  aware  he 
will  have  inflicted  an  injury  that  will  be  difficult  to  repair. 
A  small  amount  of  experience — that  which  is  essential  in  the 
proper  performance  of  every  nice  operation — will  enable  almost 
any  one,  even  those,  to  use  a  common  expression,  '  whose  fingers 
are  all  thumbs,'  to  finish  their  work  in  about  one-eighth  of  the 
time  that  the  most  expert  workman  would  require  for  the 
accomplishment  of  the  same  by  the  old  method."* 

In  the  final  adjustment  of  the  finished  piece  to  the  mouth, 
and  after  any  additional  change  in  the  form  of  the  teeth  neces- 
sary to  secure  the  most  perfect  antagonism  has  been  made,  the 
patient  should,  in  all  cases  of  partial  dentures,  receive  explicit 
directions  in  regard  to  the  general  care  and  management  of  the 
appliance  and  the  remaining  natural  teeth.  Ordinarily,  there 
will  be  but  little  difficulty  experienced  by  the  patient  in  the 
immediate  and  successful  use  of  a  substitute  supported  in  the 
mouth  by  clasps,  or  any  equivalent  means,  but  in  the  case  of 
atmospheric  pressure  plates,  the  patient  should  be  candidly 
advised  of  the  probable  want  of  stability  incident  to  the  first 
use  of  the  appliance,  and  the  consequent  annoyance  which  in 
many  cases  follows  its  occasional  displacement  in  mastication 
until  such  time  as  the  adaptation  of  the  several  parts  to  each 
other  are  perfected,  and  the  patient  has  acquired  a  habit  of 
controlling  and  directing  the  forces  applied  to  the  substitute. 
The  time  necessary  to  accomplish  these  results  will  depend 
much  upon  the  form  and  condition  of  the  mouth,  a  favorable 
or  unfavorable  antagonism,  the  adaptation  of  the  plate,  and 
the  aptitude  and  temper  of  the  patient.  It  will  be  prudent 
and  but  just  to  the  patient  to  state  that  the  complete  utility 
of  an  appliance  sustained  by  atmospheric  pressure  will  not, 
probably,  be  realized  in  less  time  than  from  four  to  six  weeks ; 
and  this  estimate  of  time,  in  a  majority  of  cases,  will  be  fully 
justified  by  experience  in  the  cases  under  consideration. 

*  Dental  Cosmos,  vol.  i,  p.  330. 


SELECTING    AND    ARRANGING    THE   TEETH.  245 

The  importance  of  thorough  and  absolute  cleanliness  of  the 
substitute  and  natural  teeth,  and  the  reasons  therefor,  should 
be  clearly  stated ;  and  the  comfort,  utility,  and  durability  of 
the  artificial  fixture  as  well  as  the  safety  of  all  the  remaining 
natural  organs  will  depend,  in  a  great  measure,  upon  the 
fidelity  of  the  patient  with  respect  to  the  observance  of  these 
injunctions.  In  those  cases  especially  where  clasps  are  used, 
the  substitute  should  invariably  be  removed  after  each  meal 
and  cleansed,  while  the  teeth  clasped  should,  at  the  same  time, 
be  freed  from  deposits  of  food  or  other  foreign  substances 
with  a  brush,  or  any  of  the  means  usually  recommended  for 
the  purpose. 


246  MECHANICAL   DENTISTRY. 


CHAPTER  XI. 
Entiee  Dentures. 

Method  of  Constructing  a  Plate  Base  for  a,n  Entire  Denture 
for  the  Upper  Jaio. — The  general  form  and  dimensions  of  the 
required  base  to  be  used  as  a  support  for  a  complete  denture 
for  the  upper  jaw  may  first  be  indicated  by  drawn  lines  upon 
the  plaster  model,  and  a  sheet-lead  pattern  obtained  from  this 
to  serve  as  a  guide  in  securing  the  form  of  the  plate  to  be 
swaged.  Whenever  the  substitute  for  the  upper  jaw  is  de- 
signed to  be  retained  in  situ  by  the  external  pressure  of  the 
atmosphere,  and  especially  where  a  central  air-chamber  is 
employed,  the  plate  should  be  made  sufficiently  ample  in  its 
dimensions  to  cover  all  the  hard  palate,  the  alveolar  ridge,  and 
all  portions  of  the  external  borders  of  the  latter  not  directly 
encroached  upon  by  the  muscles  and  reflected  portions  of  the 
mucous  membrane  of  the  lips  and  cheeks. 

Before  swaging,  the  plate  should  be  well  annealed,  and  its 
central  portion  brought  as  nearly  as  possible  to  the  form  of 
the  palatal  face  of  the  die  with  the  mallet,  forcing  the  heel  of 
the  plate  down  in  advance  of  the  portion  covering  the  more 
anterior  concavity  of  the  arch,  preventing  thereby  a  doubling 
of  the  posterior  edge  of  the  plate  upon  itself.  This  central 
portion  may  also  be  forced  more  perfectly  into  adaptation 
with  a  partial  counter  before  swaging  in  the  ordinary  manner, 
and  this  is  advisable  in  all  cases  when  the  palatal  arch  is  very 
deep ;  but  as  this  is  very  liable  to  be  drawn  from  the  arch  in 
the  process  of  turning  the  borders  of  the  plate  over  upon  the 
ridge,  a  useful  contrivance  has  been  invented  by  Dr.  Rurras, 
of  Xew  York,  to  prevent  the  displacement.  Fig.  102  shows 
the  form  of  this  instrument.  The  die  and  plate  are  placed  near 
the  edge  of  the  bench,  and  the  upper  part  of  the  clamp  adjusted 


ENTIRE   DENTURES.  247 

over  the  central  portion  of  the  plate ;  the  two  pieces  are  then 
bound  firmly  to  the  bench  by  tightening  the  screw  underneath. 
A  protective  piece  of   buckskin,   cloth,  or  paper,  should  be 
placed  between  the  plate  and  clamp,  to  prevent  the  former  from 
being  bruised  or  indented.     The  margins  of  the  plate  are  now 
turned  over  upon  the  ridge,  and  if  the  external  borders  of  the 
latter  are  undercut   or  stand  even  verti- 
cally,  the  edges  of  the  former  will  tend  to 
double  upon    themselves  at  such  points, 
and    hence    it    will    be    necessary,  before 
swaging,  to  split  the  plate  in  front,  and, 
in  some  cases,  on  each  side,  and  wherever 
divided,  a  V-shaped  piece  may  be  cut  out 
of  sufficient  "svidth  to  allow  the  divided 
edges  to  overlap  slightly  when  approxi- 
mated in  the   process  of  swaging.     The 
proximate  edges  of  the  divided  sections 
should    be   filed    to   a   thin    edge   before 
swaging,  so  that  when  brought  together 
and  soldered  there  will  be  but  little  additional  thickness  of  the 
plate  at  such  points.     The  cut  portions  should  not  be  soldered 
until  after  a  partial  or  complete  swaging. 

Having  conformed  the  plate  as  nearly  as  practicable  to  the 
die  with  the  mallet  and  pliers  (Fig.  103),  or  with  plate  forceps 
constructed  for  the  purpose  (Fig.  104),  it  should  be  placed 
between  the  die  and  counter,  and  the  latter  forced  together 
with  a  heavy  hammer  until  a  tolerably  accurate  coaptation  of 
the  plate  is  obtained,  the  latter  being  frequently  annealed 
during  the  process  of  stam])ing  to  render  it  more  pliable.  At 
first  considerable  yielding  and  consequent  deformity  of  the 
counter-die  will  occur ;  hence,  after  partial  swaging,  another 
should  be  substituted  and  the  process  continued  until  the 
greatest  possible  accuracy  of  adaptation  is  secured.  If  the  face 
of  the  die  is  marked  by  prominent  and  sharply  defined  rugie, 
or  other  irregularities,  such  points  will,  to  some  extent,  be 
bruised  or  flattened;  it  will  therefore  be  expedient  in  such 
cases,  and  better  perhaps  in  all,  to  finish  the  swaging  with  a 


248 


MECHANICAL   DENTISTEY. 


new  and  unused  die  and  counter,  in  which  case  two  or  three 
moderate,  steady,  and  well-directed  blows  of  the  hammer  will 
be  sufficient. 

If  the  plate  is  brought  into  uniform  contact  with  all  parts 
of  the  face  of  the  die,  this  conformity  is  the  only  reliable  test 


Fig.  103. 


of  its  adaptation  out  of  the  mouth.  In  no  case  will  the  swaged 
plate  fit  the  plaster  model  perfectly,  inasmuch  as  the  unavoid- 
able contraction  of  the  die,  however  slight,  will,  especially  in 
deep-arched  mouths,  cause  the  plate  to  bind  on  the  posterior 


Fig.  104. 


and  external  borders  of  the  ridge,  preventing  it  from  touching 
the  floor  of  the  palate ;  while  the  bruising,  though  inconsider- 
able, of  the  more  prominent  points  upon  the  die,  and  a  corre- 
sponding flattening  of  the  plate  at  such  points,  will  prevent 
uniform  contact  of  the  latter  with  the  unchanged  surface  of 
the  plaster  model. 


EXTIRE    DENTURES.  249 

After  final  swaging,  the  plate  should  be  again  annealed  with 
a  heat  nearly  or  quite  equal  to  that  which  will  be  ultimately 
required  in  soldering ;  after  this  any  additional  swaging  should 
be  avoided,  unless  the  plate  warps  in  the  heat,  and  which  may 
be  determined  by  applying  it  to  the  die;  if  any  change  has 
occurred,  it  should  be  re-swaged  and  again  annealed  at  a  high 
heat,  and  the  operation  should  be  repeated,  if  necessary,  until 
the  plate  retains  its  integrity  of  form  after  the  last  annealing. 
This  process  of  final  heating  does  not  apply  to  silver  if  in  the 
form  of  a  swaged  plate,  as  this  metal  invariably  suffers  some 
change  of  form  when  subjected  to  an  annealing  heat. 

Modifications  in  the  Form  of  Plates  for  Entire  Upper  Den- 
tures.— Whenever  a  central  air-chamber  is  employed,  it  may 
be  constructed  in  either  of  the  ways  described  when  treating  of 

Fig.  105.  Fig.  106. 


partial  atmospheric  pressure  plates.  The  general  form  of  a 
plate  for  an  entire  upper  denture,  with  a  central  chamber,  is 
exhibited  in  Fig.  105.  Other  modifications  in  the  form  of  cavity 
plates  for  full  upper  sets  are  in  limited  use,  as  where  chambers 
are  arranged  one  on  each  side  of  the  sloping  walls  of  the  palate, 
or  directly  over  that  portion  of  the  ridge  previously  occupied  by 
the  anterior  molar  and  the  bicuspids  on  each  side,  as  seen  in 
Fig.  106,  called  "  Lateral  Cavity  Plates."  Dr.  M.  Levett,  of 
New  York,  has  recently  introduced  another  modification  of 
cavity  plate,  consisting  of  a  number  of  small  air-chambers 
arranged  directly  over  the  ridge  and  placed  at  short  intervals 
througiiout  the  entire  border.  It  is  claimed  that  plates  con- 
structed in  either  of  the  ways  last  mentioned  cohere  with  equal 


250  MECHANICAL    DENTISTRY. 

firmness  to  the  jaw,  and  are  less  liable  to  "  rock  "  in  the  mouth, 
than  when  formed  with  a  central  chamber.  Whatever  their 
general  utility  may  be,  cases  doubtless  occur  where  they  may 
be  advantageously  employed,  as  when  any  great  inequality 
exists  in  the  hardness  of  the  ridge  and  palate,  and  a  plate  con- 
structed in  the  ordinary  manner  is  dislodged  by  "riding"  upon 
the  hard  palate  when  forces  are  applied  to  the  ridge  on  either  side. 

It  has  been  recommended,  after  having  constructed  a  base  of 
the  form  represented  in  Fig.  105,  to  cut  through  the  plate  im- 
mediately in  front  of  the  central  chamber,  making  an  opening 
of  a  semilunar  form.  It  is  claimed  that,  by  the  more  ready 
application  of  the  tongue  to  this  part,  the  air  contained  in  the 
chamber,  when  the  plate  is  applied  to  the  mouth,  may  be 
more  easily  and  thoroughly  exhausted.  There  is  great  danger, 
however,  of  the  soft  tissues  being  drawn  into  the  opening,  in 
which  case  it  can  scarcely  fail  to  produce  injury  to  the  parts 
implicated ;  the  expedient,  therefore,  is  seldom  resorted  to. 

There  is  still  another  form  of  cavity  plate  known  as  Cleve- 
land's modification  of  air-cliamber,  and  which  is  constructed  in 
the  following  manner :  A  plate  like  that  exhibited  in  Fig.  105 
is  first  struck  up  and  the  chamber  cut  out.  A  thin  sheet  of 
wax^  or  a  layer  of  plaster,  is  then  placed  upon  the  lingual  side 
of  the  plate,  extending  from  two  to  three  or  four  lines  from  the 
edges  of  the  orifice  in  the  main  plate ;  a  thin,  retreating  edge  is 
given  to  the  wax  or  plaster  at  the  outer  borders,  making  it  con- 
tinuous with  the  surface  of  the  plate.  The  plate  with  the  wax 
attached  may  now  either  be  tacked  to  the  model  with  softened 
wax  along  its  outer  borders,  and  shaped  in  such  a  way  as  to 
permit  the  model  and  plate  to  be  withdrawn  from  the  sand,  and 
a  mould  of  the  parts  taken  in  the  ordinary  way,  and  from  this 
a  die  and  counter ;  or  an  impression  in  wax  or  plaster  may  be 
taken  of  the  lingual  face  of  the  plate  and  wax,  and  afterwards 
a  model,  die,  and  counter.  With  the  latter,  a  second  plate, 
covering  nearly  or  quite  all  of  the  palatal  concavity,  is  swaged, 
and  when  this  is  applied  to  the  main  plate  over  the  cut  cham- 
ber, and  united  by  soldering,  a  space,  equal  to  the  thickness  of 
the  wax  or  plaster  placed  on  the  primary  plate,  will  be  found 


ENTIRE    DENTURES.  251 

to  exist  between  the  two  laminse.  Fig.  107  exhibits  a  trans- 
verse section  of  the  two  plates,  disclosing  the  space  between 
them,  and  also  the  opening  through  the  gum  plate  into  the 
cavity.  Before  soldering  on  the  duplicate  plate,  a  half-round 
wire  should  be  soldered  around  the  opening  in  the  palatal 
plate  on  its  lingual  side,  to  protect  the  soft  tissues  of  the  mouth 
from  injury  when  drawn  in  as  the  air  is  exhausted  from  the 
chamber ;  or,  what  is  preferable,  this  form  of  cavity  may  be 
converted,  practically,  into  what  is  known  as  "  Gilbert's  cham- 
ber" (which  is  the  central  swaged  chamber  before  described), 
by  filling  in  the  space  between  the  two  plates  with  some  im- 
pervious substance,  as  Hill's  filling,  or  an  amalgam  of  gold, 
the  excess  of  mercury  being  driven  off  by  heat.  In  the  con- 
struction of  continuous  gum  work,  the  interspace  may  be  filled 
in  with  gum  body.     The  advantages  of  these  double  plates  are, 


a  greatly  increased  strength  imparted  to  the  base,  a  diminished 
liability  of  warping  in  the  process  of  soldering,  a  smoother  sur- 
face presented  to  the  tongue,  and  a  more  decidedly  angular 
form  of  tlie  chamber. 

In  whatever  way  the  plate  is  formed,  a  notch  or  fissure  of 
sufficient  depth  to  receive  and  permit  an  unobstructed  play 
of  the  frtenum  of  the  lip  should  be  formed  in  the  front  part 
of  the  plate,  while  the  borders  of  the  latter  nearly  opposite 
the  anterior  molars  on  each  side  should  be  narrowed  to  pre- 
vent un<]ue  contact  of  its  edges  with  the  folds  of  the  mucous 
membrane  stretching  obliquely  across  from  the  cheeks  to  the 
jaw.  Care  should  also  be  taken  to  trim  away  from  the  heel 
of  tlie  i)late  any  portions  that  might  otherwise  encroach  upon 
the  soft  palate. 


252  MECHANICAL   DENTISTRY. 

It  is  only  in  the  fewest  number  of  cases  that  a  rim  can  be 
swaged  to  form  a  groove  or  socket  properly  situated  for  the 
reception  of  the  plate  extremities  of  either  single  gum  or 
block  teeth,  as  it  will  usually  be  found  impracticable  to  adjust 
the  gum  extremities  to  the  socket  thus  formed  without  neces- 
sitating, in  some  degree,  a  departure  from  a  just  arrange- 
ment and  antagonism  of  the  teeth.  Whenever  it  is  thought 
best,  therefore,  to  rim  the  plate,  it  will  generally  be  necessary 
to  adjust  and  solder  a  separate  strip  to  the  plate  along  the  plate 
ends  of  the  teeth  after  the  arrangement  of  the  latter  on  the 
base  is  completed. 

After  the  plate  has  been  worked  as  nearly  as  possible  into 
the  required  form,  it  should  be  applied  to  the  mouth  of  the 
patient  to  ascertain  the  correctness  of  its  adaptation  to  the  parts 
before  proceeding  further  with  the  operation.  If  the  adapta- 
tion is  found  imperfect,  the  fault  lies  either  in  the  impression, 
or  in  undue  contraction  of  the  die.  In  the  former  case,  another 
impression  should  be  taken,  and  the  plate  re -swaged;  in  the 
latter,  a  less  contractile  metal  or  compound  should  be  employed 
in  the  formation  of  the  die.  To  determine  the  practical  effi- 
ciency of  the  adaptation  and  adherence  of  an  atmospheric  pres- 
sure plate,  various  tests  may  be  applied.  The  coaptation  of 
its  borders  to  the  external  walls  of  the  ridge  may  be  ascertained 
by  inspection,  and  the  patient's  sense  of  contact  or  non-contact 
of  its  central  portion  with  the  floor  of  the  palate  may,  in  some 
degree,  be  relied  on  as  evidence  of  the  accuracy  of  its  adjust- 
ment to  parts  not  visible.  The  tenacity  with  which  the  plate 
adheres  on  the  application  of  direct  traction  cannot  always  be 
relied  upon,  inasmuch  as  a  well-fitting  plate  will  sometimes  be 
readily  dislodged  in  this  manner,  while,  on  the  contrary,  one 
but  illy  adapted  to  the  parts  may  require  considerable  force  to 
separate  it  from  the  jaw  when  acted  on  in  the  same  way.  The 
most  trustworthy  test  of  actual  or  practical  stability  is  firm 
pressure  applied  alternately  over  the  ridge  on  each  side  and  in 
front.  If  the  plate  maintains  its  position  and  remains  fixed 
under  repeated  trials  of  pressure  applied  in  the  manner  indi- 
cated, the  adaptation  may  be  safely  relied  on ;  if  it  slides  upon 


ENTIRE    DEXTURES.  253 

the  palate  or  is  easily  disengaged  from  the  mouth,  the  insta- 
bility of  the  plate  may  be  referred  in  many  cases,  not  to  a  want 
of  coaptation,  but  to  a  want  of  uniformity  in  the  condition  of 
the  parts  on  which  the  plate  rests.  Thus,  for  example,  if  the 
ridge  along  the  mesial  line  of  the  palatal  vault  is  more  than 
usually  prominent  and  incompressible,  and  the  alveolar  ridge 
relatively  soft  and  yielding,  the  plate,  meeting  with  a  fixed 
point  of  resistance  at  the  floor  of  the  palate,  will  prevent  the 
ridge  from  being  sufficiently  compressed  when  the  atmosphere 
is  exhausted  from  underneath  the  plate ;  and  hence,  when 
forcible  pressure  is  made  on  one  side  over  the  ridge,  the  plate, 
riding  upon  the  resistant  surfoce  of  the  arch,  will  be  thrown 
off  from  the  opposite  side.  Whenever,  therefore,  the  condi- 
tions alluded  to  prevail  to  any  considerable  extent,  a  perfect 
coaptation  of  the  plate  to  the  parts,  instead  of  favoring  the 
retention  of  the  former,  will  impair  its  stability  for  all  practi- 
cal purposes.  The  remedy  is  found  in  so  constructing  the 
plate  that,  when  adjusted  to  the  mouth,  and  before  the  air  is 
exhausted,  a  greater  or  less  s])ace  will  exist  between  the  central 
portion  of  the  plate  and  palate,  but  which,  when  a  vacuum 
is  formed,  will  be  carried  up  into  contact  with  the  roof  of  the 
mouth,  and  at  the  same  time  compress  the  ridge  sufficiently  to 
afford  a  firm  and  resisting  basis  for  the  plate  in  mastication. 
This  peculiar  adaptation  of  the  plate  may  be  obtained  by  ad- 
justing a  piece  of  sheet-lead  or  wax  plate  over  the  central  ridge 
on  the  plaster  model,  by  means  of  which  the  corresponding 
portion  of  the  plate,  when  swaged  with  a  die  obtained  from  the 
model  so  prepared,  will  be  thrown  far  enough  from  the  roof 
of  the  mouth  to  answer  the  purpose  before  indicated.  This 
will  be  more  particularly  necessary  in  shallow  arches ;  while, 
if  the  arch  is  very  deep,  or  even  moderately  so,  the  unavoidable 
contraction  of  the  die  may  render  the  expedient  unnecessary. 

Method  of  Construdinrj  a  Plate  Bern;  for  an  Entire  Devture 
for  the  Under  Jav\ — Aside  from  the  differences  in  the  form  of 
the  plate,  and  the  manipulations  incident  thereto,  the  process 
of  constructing  a  plate  for  the  under  jaw  does  not  differ  essen- 


254  MECHANICAL   DENTISTRY. 

tially  from  that  already  described  in  connection  with  full 
upper  dentures. 

If  the  lower  plate  is  constructed  from  a  single  lamina  of  gold 
or  other  metal,  it  should  be  somewhat  thicker  than  that  used 
in  upper  cases,  and  should  also  be  of  finer  quality,  as  the  addi- 
tional thickness  of  the  plate  and  the  peculiar  form  of  the  in- 
ferior maxilla  renders  a  greater  degree  of  pliancy  necessary  in 
swaging  it  to  the  form  of  the  ridge.  The  general  form  of  a 
base  for  an  entire  lower  denture  is  exhibited  in  Fig.  108.  The 
internal  border  of  the  plate  should  usually  be  doubled, — either 
by  turning  the  edge  over  in  swaging,  or  by  soldering  on  a  narrow 
strip  of  plate  or  half-round  wire. 

A  more  perfect  adaptation  of  the  plate  to  the  ridge  may  be 
obtained  by  the  use  of  a  double  instead  of  a  single  plate,  in 

Fig.  108.  Fig.  109. 


which  case  a  thin  basement  plate,  not  exceeding  No.  30  of  the 
gauge,  should  be  swaged  to  the  form  of  the  ridge  in  the  first 
instance,  and  then  a  duplicate  plate,  swaging  the  two  together 
and  uniting  them  to  each  other  with  solder.  A  plate  of  the 
specified  thickness  may  be  very  readily  and  accurately  con- 
formed to  any  irregularities  in  the  ridge,  and  when  the  two  are 
united  the  base  will  be  heavier  and  stronger  than  a  single 
lamina  of  the  ordinary  thickness.  Instead,  however,  of  dou- 
bling the  entire  plate,  it  will  be  sufficient,  in  most  cases,  to  adapt 
the  second  plate  only  to  the  lingual  surface  of  the  first,  extend- 
ing it  up  from  the  lower  edge  to  a  point  corresponding  as 
nearly  as  possible  with  the  posterior  portions  of  the  base  of  the 


ENTIRE   DENTURES.  255 

teeth  when  the  latter  are  adjusted  to  the  plate  (Fig.  109).  A 
moderately  thhi  plate  may,  in  this  manner,  be  used  for  the 
primary  base,  while  the  duplicate  band  will  impart  the  requi- 
site strength  to  the  plate,  and,  at  the  same  time,  obviate  the 
necessity  of  wiring  its  inner  edges.  In  adopting  either  of  the 
last-named  methods,  the  plates  after  they  are  united  to  each 
other,  should  be  again  swaged  to  correct  any  change  of  form 
incident  to  the  use  of  solder. 

Antagonizing  Ilodel  for  an  Entire  Upper  and  Lower  Den- 
ture.— Either  of  the  following  methods  may  be  adopted  in  se- 
curing an  antagonizing  model  for  complete  dentures : 

1.  Attach  to  the  ridge  of  each  plate  a  roll  or  strip  of  adhesive 
wax  corresponding  in  widtli  to  the  length  of  the  teeth  which 
will  be  required  for  each  plate  respectively ;  place  the  plates 
with  the  wax  attached  in  the  mouth,  and  trim  away  from  the 
proximate  edges  of  the  wax  until  the  two  sections  close  upon 
each  other  uniformly  throughout  the  circle;  then  cut  away 
from  the  labial  surfaces  of  the  rims  of  wax,  above  and  below, 
until  the  proper  fulness  and  required  contour  of  the  parts  asso- 
ciated with  the  lips  and  mouth  are  secured.  The  approxima- 
tion of  the  two  jaws,  when  the  finished  substitutes  are  ulti- 
mately adjusted  to  the  mouth,  will  depend  altogether  upon  the 
aggregate  width  given  to  the  two  sections  of  wax  at  this  stage 
of  the  operation,  and  it  is,  therefore,  important  that  the  "  bite  " 
or  closure  of  the  jaws  secured  at  this  time  should  be  such  as 
will  most  perfectly  fulfil  the  requirements  of  the  case  in  respect 
to  the  utility  and  comfort  of  the  appliance,  and  the  proper 
restoration  of  the  required  facial  proportions.  If  there  is  any 
considerable  change  produced  in  the  relation  of  the  jaws  habit- 
ual to  them  })rior  to  the  loss  of  the  natural  teeth,  the  charac- 
teristic expression  of  the  individual  will,  in  some  degree,  be 
changed  or  marred  ;  an  unaccustomed  and  restrained  action 
will  be  imposed  ui)on  the  muscles  concerned  in  the  movements 
of  the  lower  jaw,  which  will  render  the  use  of  the  appliances 
at  least  temporarily,  if  not  permanently,  uncomfortable  and 
fatiguing,  or  even  j)ainrid  ;  while  the  utility  of  the  fixtures 
may  be  impaired  or  wholly  destroyed,  by  compelling  a  partic- 


256  MECHANICAL   DENTISTRY. 

ular  application  of  forces  in  mastication  inconsistent  with  their 
stability  in  the  mouth.  No  specific  directions,  of  course,  can 
be  given  that  will  apply  to  all  cases,  but  it  may  be  observed 
that,  ordinarily,  the  two  sections  of  wax  should  be  cut  away 
from  their  approxinating  surfaces  until  the  jaws  close  suffi- 
ciently to  permit  the  edges  of  the  lips  to  rest  easily  and  natu- 
rally upon  each  other  when  in  a  relaxed  condition,  or  the 
upper  rim  may  extend  somewhat  below  the  margin  of  the 
up2)er  lip,  while  the  lower  section  of  the  wax  is  cut  away  on  a 
level  with  the  lower  lip,  or  a  little  below  it.  Cases  occur, 
however,  where  a  less  exposure  of  the  upper  portion  of  wax, 
even  though  quite  narrow,  will  be  required;  as  where  the 
alveolar  ridge  is  very  deep,  and  the  lip  covering  it  either  abso- 
lutely or  relatively  short,  or  where  the  latter  is  retracted, 
exposing,  even  when  in  a  state  of  repose,  a  greater  portion  or 
all  of  the  crowns  of  the  teeth,  and  in  extreme  cases  the  mar- 
gins of  the  gum.  Between  the  latter  extreme  and  an  inordi- 
nate extension  of  the  upper  lip  below  the  ridge  all  intermediate 
conditions  occur,  and  the  practitioner,  aiming  to  produce  an 
agreeable,  harmonious,  and  truthful  expression  of  all  the  parts, 
must  rely  wholly  upon  his  judgment  in  reference  to  the  neces- 
sary approximation  of  the  jaws,  the  restoration  of  the  natural 
fulness  and  contour  of  the  mouth,  and  the  relative  length  to  be 
given  to  the  upper  and  lower  teeth. 

Patients,  when  requested  to  close  the  mouth  naturally,  are 
very  liable  to  j)roject  the  under  jaw ;  hence  it  is  well  to  have 
them  open  and  close  the  jaws  frequently,  observing,  at  the 
same  time,  if  the  separate  portions  of  wax  meet  in  precisely  the 
same  manner  at  each  occlusion.  If  the  bite  varies  at  every 
approximation  of  the  jaws,  the  patient  should  be  directed  to 
relax  and  abandon  for  the  moment  all  control  over  the  muscles 
of  the  lower  jaw ;  the  operator  should  then  grasp  the  chin  and 
press  the  jaw  first  directly  backward  and  then  upward  until 
the  opposing  surfaces  of  the  wax  meet,  in  which  po&ition  it 
should  be  steadily  held  by  the  patient  until  the  two  portions  of 
wax  are  attached  to  each  other  in  that  particular  relation. 
The  latter  may  be  done  by  drawing  lines  vertically  across  the 


ENTIRE    DENTURES.  257 

rims  of  wax  at  various  points  "wliicli  will  serve  to  indicate  their 
relation  to  each  other  when  out  of  the  mouth ;  or  a  heated 
knifeblade  may  be  passed  between  the  two  sections,  the  melted 
wax  temporarily  uniting  them.  A  very  convenient  and  secure 
method  is  to  attach  them  together  by  means  of  two  strips  of 
metal  bent  in  the  form  of  a  stajile;  these  may  be  warmed  in  a 
spirit-flame,  and  pressed  into  the  wax,  one  on  each  side — one 
end  penetrating  the  upper  rim  of  wax,  the  other  the  lower. 
Before  removing  the  plates,  the  mesial  line  of  the  mouth 
should  be  indicated  upon  the  wax  by  drawing  a  line  vertically 
across  the  latter  in  front  to  serve  as  a  ffuide  in  the  arrano-ement 
of  the  central  incisors. 

2.  Another  method  is  to  attach  to  either  the  upper  or  lower 
plate  a  single  rim  of  wax  somewdiat  wider  than  will  be  required 
for  both  the  upper  and  lower  teeth.  The  plates  are  then  placed 
in  the  mouth,  and  the  jaws  brought  together,  imbedding  the 
opposite  plate  in  the  wax.  When  this  method  is  adopted,  the 
proper  closure  of  the  jaws  is  best  determined  by  a  gauge  or 
guide  consisting  of  .a  strip  of  plate  or  other  substance  encased 
in  the  wax  and  interposed  edgewise  between  the  borders  of  the 
two  plates  in  front  in  such  manner  that,  when  the  latter  are 
approximated,  they  will  close  upon  the  guide,  the  desired  rela- 
tion of  the  jaws  to  each  other  having  been  previously  ascer- 
tained by  trial  of  the  guide  with  the  plates  in  the  mouth  before 
adjusting  the  wax.  The  exterior  surface  of  the  wax  rim  is 
then  trinmied  away,  or  additional  portions  added  to  it,  until 
the  proper  fulness  and  contour  are  given  to  the  lips;  after 
which  the  medium  line  of  the  mouth  should  be  traced  upon 
the  wax  in  front,  as  before  described. 

The  plates,  attached  to  each  other  in  either  of  the  ways 
mentioned,  having  been  removed  from  the  mouth,  a  batter  of 
plaster  may  be  poured  upon  a  piece  of  paper  or  other  substance, 
forming  a  layer  a  fourth  or  a  half  an  inch  thick  and  two  or 
three  inches  long,  when  the  under  surface  of  the  lower  plate 
may  be  imbedded  in  one  end  of  the  plaster,  and  the  remaining 
portion  of  the  latter  projecting  from  the  heel  of  the  plate 
trinnned  and  formed  for  articulating  with  the  second  piece  of 

]7 


258  MECHANICAL   DENTISTRY. 

the  antagonizing  model  in  the  same  manner  as  described  when 
considering  partial  dentures.  The  entrance  to  the  cavity  be- 
tween the  two  plates  is  now  closed  up  with  a  sheet  of  softened 
wax  or  otherwise,  and  the  whole  surrounded  by  a  piece  of  oil- 
cloth, wax,  or  other  substance,  and  the  second  part  of  the  model 
obtained  by  pouring  plaster  in  upon  the  exposed  surface  of  the 
upper  plate  and  the  plaster  posteriorly  to  the  depth  of  half  an 
inch  or  more.  When  the  plaster  is  sufficiently  condensed,  the 
line  across  the  wax  in  front  should  be  extended  in  a  direct  line 
across  the  borders  of  the  plaster  model  above  and  below,  as,  in 
arranging  the  teeth,  the  wax  will  be  cut  away,  and  without 
this  precaution  the  mesial  point  of  the  mouth  may  be  lost. 
The  form  of  an  antagonizing  model  for  an  entire  upper  and 

Fig.  110. 


lower  denture,  with  the  plates  and  wax  attached,  the  latter 
being  cut  away  somewhat  preparatory  to  adjusting  the  teeth, 
is  shown  in  Fig;.  110. 

Antagonizing  3Iodel  for  an  Mitire  Upper  Denture  with  the 
Natural  Teeth  of  the  Lower  Jaw  Remaining. — In  forming  an 
antagonizing  model  to  be  used  as  a  guide  in  arranging  and  ar- 
ticulating a  full  upper  denture  where  all  or  a  part  of  the 
natural  organs  of  the  inferior  jaw  are  remaining,  a  rim  of  wax 
should  first  be  adjusted  to  the  borders  of  the  plate,  one  or  two 
lines  wider  than  the  required  length  of  the  artificial  teeth. 
When  j)laced  in  the  mouth,  the  exterior  surface  of  the  wax 
draft  should  be  cut  away  or  added  to,  until  the  proper  fulness 
of  the  parts  is  restored.  The  patient  should  then  close  the 
lower  teeth  against  the  wax,  imbedding  them  just  sufficiently 
to  indicate  the  cutting  edges  and  grinding  surfaces  of  the 
opposing  teeth.     If  a  fuller  impression  of  the  exterior  faces  of 


ENTIRE    DENTURES. 


259 


the  lower  teeth  are  required,  it  may  be  obtained  by  pressing  in 
a  small  strip  of  softened  wax  against  them  and  the  lower  edge 
of  the  rim  of  wax  upon  the  plate ;  or  the  projecting  borders 
of  the  latter  may  be  forced  down  upon  the  crowns  with  the 
fingers.  The  median  line  of  the  mouth  is  then  indicated  upon 
the  wax,  the  plate  removed,  and  its  palatal  surface  imbedded 


FiCx.  111. 


in  one  end  of  a  layer  of  plaster  spread  upon  a  strip  of  paper; 
the  portion  of  plaster  extending  from  the  heel  of  the  plate 
trimmed,  grooved,  varnished  and  oiled;  the  entire  piece  in- 
closed, and  plaster  ])oured  in  upon  the  exposed  surfaces  of  the 
wax  and  plaster  to  the  depth  of  one-fourth  or  one-half  of  an 
inch.     The  two  sections  of  the  model,  with  the  plate  and  wax 


Fig.  112. 


attached,  the  latter  being  cut  away  somewhat  to  receive  the 
porcelain  teeth,  is  exhibit(;d  in  Fig.  111. 

Various  articulators,  or  antagonizing  frames,  have  been  de- 
vised, and  may  be  substituted  for  the  plaster  articulator  just 
described.  A  very  excellent  adjustable  contrivance  of  the  kind, 
invented  by  Dr.  Hayes,  is  exhibited  in  Fig.  112.     Witii  this 


260  MECHANICAL    DENTISTRY. 

appliance,  all  the  motions  of  the  jaws  can  be  represented,  and 
the  relative  positions  again  brought  back  at  pleasure  at  the 
starting-point.  The  screw  hinge  admits  lateral  motion.  The 
set  screv/  on  the  side  plays  into  a  slot,  securing  one  central 
position,  to  which  it  can  at  all  times,  when  desired,  be  brought 
back.  The  long  screw  in  the  foot  produces  back  and  forward 
motion,  the  main  hinge  up  and  down  motion,  and  the  large 
nut  on  the  bottom  renders  all  the  parts  taut  and  unyielding. 

Considerable  space  is  here  devoted  to  the  consideration  of  an 
ingenious  and  novel  device,  introduced  to  the  notice  of  the  pro- 
fession by  Dr.  W.  G.  A.  Bonwill,  of  Philadelphia,  Pa.,  and 
characterized  by  him  as  the 

"  Anatomical  Articulator." 

As  to  the  character  of  this  instrument,  the  author  cannot 
speak  personally.  Dr.  B.,  whose  name  is  inse])arably  connected 
with  the  electric  mallet,  dental  engine,  original  methods  of 
attaching  pivot  crowns  described  elsewhere,  and  various  other 
practical  devices,  says  that  it  holds  the  same  positive  relation  or 
position  in  his  laboratory  as  do  the  electric  mallet  and  engine 
in  his  operating  room.  In  other  words,  it  is  indispensable  to 
the  perfect  articulation  of  all  artificial  dentures  from  one  to  a 
full  set, — that  it  is  a  sine  qua  non.     He  says : 

"  It  is  modelled  on  the  same  geometrical  system  as  the  hu- 
man jaw. 

"  I  found  by  measurement  that  the  average  width  of  the  lower 
jaw  from  centre  to  centre  of  each  condyle  was  four  (4)  inches,  and 
from  the  same  centre  of  each  condyloid  process  to  the  median 
line  of  the  lower  jaw,  where  the  cutting  edges  of  the  lower  in- 
cisors meet,  was  also  four  (4)  inches,  making  of  the  human  jaw 
an  equilateral  triangle.  This  holds  good  in  all  jaws,  and  the 
difference  of  a  quarter  of  an  inch  in  this  radius  of  a  circle  of 
four  inches  would  make  but  little  practical  difference  as  to  the 
results. 

"  This  beautiful  law  enables  us  to  have  the  fullest  benefit  of 
mastication  at  the  least  expense  of  power  and  motion  in  the 
arc  of  the  circle  of  four  inches  as  a  radius. 


ENTIRE    DENTURES.  261 

"  This  being  an  absolute  law,  I  have  so  made  this  articula- 
tor, and  the  cast  of  every  case  is  set  therein  with  tiie  median 
line  at  the  lower  centrals  just  four  (4)  inches,  by  the  dividers, 
from  each  condyloid  process.  If  an  unusually  large  jaw,  then 
the  cast  is  put  a  very  little  distance  further  out. 

"  For  all  full  sets,  the  articulation  is  so  perfect,  as  made  in 
this,  in  the  laboratory,  as  to  need  but  a  trifling  touch  in  fitting 
in  the  mouth. 

"I  found  that  there  is  a  further  positive  law  in  the  mechan- 
ism of  the  human  jaw  that  should  be  regarded  in  every  sub- 
stitute made  therefor,  and,  that  is,  just  in  proportion  to  the 
depth  of  overbite  of  the  centrals,  there  is  a  curvature  from 
the  mesial  surface  of  the  first  molars  back,  through  the  other 
molars,  up  the  ramus.  That  this  curvature  upwards .  and 
backwards  at  the  ramus  is  due  solely  to  the  depth  of  closure 
of  the  ujiper  over  the  lower  jaw.  That  where  there  is  occlu- 
sion or  closing  of  the  cutting  surfaces  of  the  incisors  directly 
upon  each  other,  then  a  straight  line,  directly  backwards,  is 
the  consequence.  If  curved  at  the  ramus,  in  such  a  case,  no 
lateral  or  forward  movement  of  the  lower  jaw  could  occur, — 
only  the  up  and  down. 

"  Where  there  is  an  eighth  of  inch  depth  of  bite,  then,  as 
you  go  back  to  the  centre  of  motion — the  condyloid  processes — 
the  cusps  in  the  bicuspids  and  molars  grow  less  deep,  and  the 
curvature  at  the  ramus  is  an  eighth  of  an  inch  out  of  line. 

"  When  there  is  an  overbite  of  an  eighth  of  an  inch,  then,  in 
opening  the  lower  jaw  and  carrying  it  forward  to  use  the  in- 
cisors for  cutting,  the  back  teeth  of  lower  jaw  are  brought  for- 
ward ;  and,  as  the  second  molar  is  higher  out  of  line  than  the 
first  molar,  it  comes  in  contact  with  the  distal  surface  of  the 
first  superior  molar,  which  begins  just  here  to  curve  u])ward, 
and  is  the  highest  out  of  line  in  the  superior  jaw,  and  they 
meet  at  same  time  that  the  incisors  do.  And  the  same  law  holds 
good  when  the  lower  j-aw  is  turned  to  the  right  or  left,  the 
molars  are  brought  in  contact  to  equalize  the  force  which 
would  be  brought  upon  the  incisors  only.     Besides,  the  recog- 


262  MECHANICAL   DENTISTRY. 

nizing  of  this  law  enables  the  cusps  or  palatal  and  lingual 
sides  of  the  molars  of  both  jaws  to  be  utilized  in  every  position 
the  lower  jaw  may  take  in  mastication.  Upon  this  plan  I 
make  all  my  artificial  dentures,  most  of  their  articulating  sur- 
faces being  utilized  at  every  position  of  the  lower  jaw.  Any 
human  jaw  will  show  this  system,  which  by  this  system  can 
be  made  just  as  complete,  and  more  so,  in  many  cases,  than 
the  normal,  or  such  as  is  found  in  advanced  civilization. 

"  When  a  set  is  commenced  in  this  articulator  with  the  up- 
per overbiting  the  lower  an  eighth  of  an  inch,  as  you  set  each 
tooth  backward  towards  the  condyloid  processes,  they  will 
assume  the  exact  angle  and  depth  of  cusps,  as  well  as  the  cur- 
vature at  the  ramus,  as  found  in  nature.     If  both  jaws  are  in 

Fig.  113. 


direct  apposition  at  the  incisors,  then  all  of  the  teeth  must  of 
necessity  be  on  a  perfect  plane,  or  but  one  would  touch  when  in 
lateral  position. 

"  With  this  one  base,  which  Fig.  114  shows,  there  is  a  sep- 
arate bow  to  each  part  of  base,  one  for  upper  and  one  for  lower 
jaw,  which  can  be  removed  as  soon  as  the  plaster  in  one  case  is 
allowed  to  harden  on  the  rim.  This  can  be  marked  and  laid 
away  for  a  year  if  necessary,  and  then  articulated.  A  pair  of 
bows  can  be  used  for  as  many  separate  cases,  while  only  one 
base  is  required,  which  should  be  made  absolutely  and  geomet- 
rically exact — approximately  so. 

"  There  is  no  need  for  set  screws  to  hold  the  bows,  as  they 


ENTIRE   DENTURES. 


263 


go  up  just  so  far  and  remain  so.  Nor  is  there  any  set  screw  and 
prop  to  hold  the  jaws  or  casts  apart.  This  is  regulated  on  the 
bite  in  wax,  which,  before  it  is  taken  off  the  base  plate,  has  the 
exact  height  marked  by  a  pair  of  dividers  on  the  plaster  at  the 
median  line,  measuring-  from  the  cutting^  edge  of  wax,  and 
then  when  the  first  central  or  block  is  set,  there  is  no  longer 
any  call  for  a  prop  to  keep  open  the  jaws  of  the  articulator. 
When  this  height  is  taken  with  the  dividers,  it  is  marked  on 
the  top  of  each  cast  for  future  reference.  It  would  interfere 
with  the  lateral  movement  if  a  rigid  prop  were  there.  The 
dividers  make  each  case  exact  without  a  scale  for  measurement. 


"  Articulate  the  upper  set  first,  and  retain  on  the  lower  base 
the  wax  for  length  and  fulness.  When  the  upper  are  all  on, 
then  the  lower  incisors  are  gauged  as  to  the  height  or  length 
by  the  dividers  while  the  wax  is  still  on  the  base  plate  and 
taken  from  the  height  marked  on  the  lower  cast  for  reference. 

"  Make  the  lateral  movement  as  soon  as  the  first  tooth  or 
block  is  in  position  where  the  case  is  an  upper  one  with  a  good 
lower  jaw  of  natural  teeth. 

"When  a  full  set,  the  upper  are  first  ground  on  and  shaped 
so  as  to  meet  the  intended  overbite,  and  when  the  lower  set  are 
ground  on,  tlie  uj)j)er  can  be  changed  to  suit  the  lower,  so  as  to 
allow  the  whole  of  every  cusp  to  touch  at  nearly  every  lateral 
movement  of  jaw. 

"  When  the  plaster  case  is  to  be  set  in  the  articulator,  it  must 


264  MECHANICAL   DENTISTRY. 

be  done  with  the  dividers  set  just  four  (4)  inches,  with  one  point 
at  the  median  line  as  formed  by  the  lower  incisors,  and  the 
other  carried  over  to  each  condyloid  process  as  marked  on  the 
articulator.  This  makes  the  centre  of  jaw  equidistant  from  the 
condyles.  The  study  of  this  principle  will  make  one  fully 
realize  the  beautiful  workings  of  Divinity,  which  is  only  gov- 
erned by  positive  law  in  every  department  of  the  universe. 
With  this  plan,  understand  one  will  never  again  attempt  to 
articulate  a  set  of  teeth  on  the  unwritten  law,  as  now  univer- 
sally made  and  recognized  by  every  dentist  in  the  land. 

"  Until  this  system  is  taught  in  the  schools,  and  by  private 
practitioners,  no  truly  artistic  and  fully  natural  set  of  teeth 
can  ever  be  made,  for  we  have  been  without  law  in  this  de- 
partment. To  describe  it  is  not  enough.  It  must  be  seen  and 
demonstrated,  one  tooth  at  a  time,  until  the  whole  set  is  made. 
Only  in  this  way  can  it  be  understood. 

"The  Figs.  113  and  114  show  clearly  the  simple  construc- 
tion. It  is  made  of  brass  wire  (one-eighth  inch  in  diameter), 
and  brass  tubing  to  allow  the  size  of  wire  to  fit  closely,  and 
move  freely  therein  when  drawn  out  or  pushed  up.  The  spiral 
spring  on  either  condyle  allows  of  easy  lateral  motion  to  the 
lower  part,  and  from  exactly  the  same  standpoint  as  in  nature ; 
that  is,  one  of  the  lower  condyles  moves  forward  in  the  glenoid 
cavity  while  the  other  remains  still.  Every  part  of  it  is  rigid 
except  the  movement  at  the  condyles,  and  the  joints  or  bows 
are  only  temporarily  so.  There  is  also  an  up  and  down  motion 
made  at  the  condyles  by  raising  bow  up  or  down. 

"No  case,  when  once  fixed  in  it,  can  become  disarranged. 
If  the  bite  in  the  wax  is  not  correct,  no  articulator  can  make  it  so. 
You  must  go  back  again  to  the  mouth,  and  retake  it,  'svhich  is 
easily  done  at  first  by  asking  the  patient  to  swallow,  when  the 
jaws  will  automatically  close  and  assume  their  normal  position. 
If  now  correct,  there  is  never  any  necessity  for  a  screw  to 
change  it  when  once  in  this  articulator. 

"  There  can  be  no  excuse  for  failure  or  unartistic  work  when 
this  instrument  is  once  understood,  and  the  law  controlling  the 


ENTIEE    DENTURES.  265 

human  jaw.  As  we  may  forever  have  to  resort  to  artificial 
dentures,  we  should  demand  of  the  colleges  that  such  an  instru- 
ment be  used,  and  it  alone,  as  furnishing  the  only  hope  now 
offered  of  an  approach  to  high-toned,  artistic,  mechanical  den- 
tistry. Until  we  can  be  taught  to  appreciate  that  law  is  the 
governor  of  the  universe,  and  applicable  in  every  branch  of 
dentistry,  we  are  false  men,  and  will  set  '  false  teeth,'  and  never 
realize  our  high  destiny." 

Selecting,  Arranging,  and  Antagonizing  the  Teeth;  Rimming 
the  Plate;  Attaching  Spiral  Springs ;  Investing,  Lining,  Sold- 
ering, and  Finishing. — In  selecting  teeth  for  an  entire  upper 
and  lower  denture,  the  special  requirements  in  respect  to  size, 
form,  and  color,  will  depend,  in  a  great  measure,  upon  the 
complexion,  age,  sex,  general  configuration  of  the  face,  etc., 
of  the  patient.  Every  separate  denture,  therefore,  that  is  con- 
structed in  strict  conformity  with  a  faithful  interpretation  of 
the  special  requirements  of  each  individual  case,  will  be  char- 
acterized by  shades  of  differences  in  the  color,  form,  size,  and 
arrangement  of  the  teeth  of  replacement.  It  will  be  sufficient 
in  this  connection  to  observe  that  such  selection  of  the  teeth 
should  be  made  as  will  most  perfectly  reproduce  the  lost  pro- 
portions of  the  facial  contour,  and  impart  to  the  individual  a 
natural,  harmonious,  and  agreeable  expression. 

In  arranging  or  adjusting  single  gum  teeth  to  the  plate  in 
those  cases  where  the  changes  in  the  form  of  the  alveolar  rido-e 
consequent  on  absorption,  are  completed,  the  portions  applied 
to  the  base  should  be  ground  away  sufficiently  to  restore  the 
required  fulness  of  the  parts  and  to  give  proper  length  and 
inclination  to  the  teeth.  The  coaptation  of  the  ground  sur- 
faces to  the  base  should  be  accurate  enough  to  exclude  perfectly 
particles  of  food,  an<l  to  furnish  such  a  basis  to  each  tooth  as 
will  provide  most  effectually  against  fracture  when  acted  upon 
by  the  forces  api)Hed  to  them  in  the  mouth.  The  gum  extremi- 
ties of  the  teeth  should  also  be  accurately  united  to  each  other 
laterally  by  grinding  carefully  from  their  proximate  edges 
until  the  joints  or  seams  will  be  rendered  incapable  of  ready 
detection  in  the  mouth,  care  being  taken   that  this  coaptation 


266  MECHANICAL   DENTISTRY. 

of  the  adjoining  surfaces  is  uniform,  for  if  confined  to  the  outer 
edge  alone,  portions  of  the  gum  enamel  may  be  broken  away 
iu  the  process  of  soldering. 

In  the  construction  of  substitutes  designed  to  fulfil  only  a 
temporary  purpose,  and  where  the  alveolar  processes  remain  in 
a  great  measure  unabsorbed,  and  plain  teeth  (those  represent- 
ing but  the  crowns  of  the  natural  organs)  are  used,  but  little 
skill  will  ordinarily  be  required  in  adjusting  and  fitting  them 
to  the  base.  If  the  ridge  in  front  is  prominent  and  but  inade- 
quately concealed  by  the  lip,  as  where  the  teeth  have  been  but 
recently  extracted,  all  those  portions  of  the  border  of  the  plate 
in  front,  anterior  to  the  first  or  second  bicuspid  on  each  side, 
may  be  cut  away  on  a  line  a  little  within  the  required  circle  of 
the  anterior  teeth,  and  scolloped  (Fig.  115),  permitting  the 
anterior  cervical  portions  of  the  artificial  incisors  and  canines, 
and,  in  some  cases,  the  anterior  bicuspids,  to  overlap  the  edge 
of  the  plate  and  rest  directly  upon  the  gum  in  front.  This 
abridgment  of  the  plate  will  not  ordinarily  materially  aflPect 
the  adhesion  or  stability  of  the  substitute. 

There  are  cases  of  a  mixed  character  that  render  it  more 
difficult  to  effect  a  harmonious  and  symmetrical  arrangement 
of  the  teeth,  as  where  a  limited  number  of  the  natural  teeth  at 
intervals  have  been  long  absent  and  the  excavations  in  the 
ridge  consequent  on  absorption  alternate  with  other  points 
upon  the  ridge  in  a  comparatively  unchanged  condition.  To 
give  uniformity  to  the  denture  by  restoring  perfectly  the  re- 
quired circle  of  the  arch  in  such  cases  will  necessitate  the  em- 
ployment of  plain  and  single  gum  teeth  conjointly.  When- 
ever necessary,  those  portions  of  the  base  occupied  by  the  plate 
teeth  may  be  cut  away  in  such  a  manner  as  to  permit  the  latter 
to  be  adjusted  directly  to  the  unabsorbed  gum  as  before  de- 
scribed. 

In  the  process  of  grinding  the  teeth  to  the  base,  above  and 
below,  the  operator  should  commence  by  first  arranging  the 
superior  central  incisors  and  then  the  lower,  and  so  passing 
back  from  tooth  to  tooth,  grind  and  adjust  an  upper  and  lower 
tooth  alternately,  keeping  the  upper  ones  in  advance  of  those 


EXTIRE    DENTURES. 


267 


of  the  lower  jaw.  The  central  incisors  above,  should  be  placed 
parallel  with  each  other,  but  tlie  cutting  edges  of  the  laterals, 
and  the  points  of  the  canines,  should  incline  slightly  toward 
the  medium  line  of  the  mouth.  lu  arranging  the  teeth  of  the 
upper  jaw,  the  anterior  six  may  be  made  to  describe,  with 
more  or  less  exactness,  the  segment  of  a  circle,  but  a  somewhat 
abrupt  angle  may  be  given  to  the  arch  on  each  side  by  placing 
the  first  bicuspid  within  the  circle  in  such  a  way  that,  when 
standing  directly  in  front  of  the  patient  and  looking  into  the 
mouth,  only  a  narrow  line  of  the  exterior  face  of  the  crowns  of 
these  teeth  will  be  seen,  while  the  remaining  teeth  posterior  to 
them,  should  be  arranged  nearly  on  a  straight  line,  diverging 
as  they  pass  backward.     When  arranged  in   the  manner  de- 


Fin.  Hi. 


Fig.  116. 


scribed,  the  peripheral  outline  of  the  arch  will  exhibit  some- 
what the  form  ])resented  in  the  above  diagram  (Fig.  116). 

In  regard  to  the  practical  efficiency  of  an  upper  denture  re- 
tained in  the  mouth  by  atmospheric  pressure,  it  is  important 
that  the  teeth  engaged  in  the  comminution  of  food,  as  the  bi- 
cuspids and  molai's,  should  occupy  a  position  directly  over  the 
central  line  of  the  ridge,  and  should  either  be  arranged  verti- 
cally or  with  a  slight  inclination  toward  the  centre  of  the 
mouth.  The  liability  to  displacement  of  the  substitute  in 
mastication  will  thus  be  greatly  diminished,  wherea.'!,  if  placed 
outside  of  the  line  indicated,  and  especially  with  a  diverging 
inclination,  the  stability  of  the  appliance  will  be  endangered, 


268  MECHANICAL   DENTISTRY. 

and  the  functions  of  mastication  impeded,  notwithstanding 
other  conditions  necessary  to  complete  success  hav^e  been  fully 
secured.  In  arranging  the  upper  and  posterior  teeth  as  de- 
scribed, it  will  sometimes  be  necessary  to  give  to  the  opposing 
under  teeth  a  decided  inward  inclination  in  order  to  effect  a 
satisfactory  antagonism  of  the  teeth;  and  cases  occur  where  a 
practical  articulation  cannot  be  secured  without  departing  in 
some  degree,  from  the  arrangement  of  the  upper  teeth  spoken 
of, — as  where  a  great  disparity  exists  between  the  posterior 
transverse  diameters  of  the  two  jaws,  a  medium-sized,  or  even 
small,  arch  above  being  associated  with  an  expanded  ridge 
below. 

In  articulating  the  upper  and  lower  teeth,  the  closure  or  re- 
lation of  the  natural  organs  should  be  imitated  as  nearly  as  the 
other  essential  requirements  of  the  case  will  admit  of.  Hence 
the  upi^er  front  teeth,  describing  the  segment  of  a  larger  circle 
than  the  corresponding  teeth  of  the  lower  jaw,  will  project 
beyond  and  overlap  slightly  the  cutting  edges  of  the  latter ; 
and  having  a  greater  width  of  crown,  they  will  extend  laterally 
beyond  the  opposing  teeth,  covering  one-third  of  the  crowns  of 
those  next  adjoining,  so  that  when  the  canines  of  the  upper  jaw 
are  reached,  they  will  close  between  the  lower  canines  and  first 
bicuspids ;  and,  passing  back,  the  anterior  superior  bicuspids 
between  the  first  and  second  bicuspids  below ;  the  posterior 
bicuspids  above  between  the  second  inferior  bicuspids  and  an- 
terior molars ;  the  first  superior  molars  between  the  first  and 
second  molars  below ;  while  the  anterior  half  of  the  posterior 
molars  above  will  close  upon  the  posterior  half  of  the  inferior 
second  molars,  the  remaining  posterior  half  of  the  second 
molars  above  extending  posteriorly  beyond  those  of  the  lower 
jaw.  The  outer  cusps  of  the  superior  bicuspids  and  molars 
will  overlap  those  of  the  inferior  teeth ;  while  the  inner  cusps 
of  the  teeth  of  the  superior  jaw  will  pass  into  the  depressions 
in  the  lower  teeth  formed  by  the  internal  and  external  cusps, 
and  the  external  cusps  of  the  inferior  teeth  will,  in  like  man- 
ner, be  received  into  the  corresponding  excavations  of  the  upper 
teeth.     The  relative  position  and  antagonism  of  the  teeth,  as 


ENTIRE    DENTURES.  269 

they  a})pear  in  a  regularly  arranged  denture  for  both  jaws,  are 
shown  in  Fig.  117.  An  abnormal  relation  of  the  jaws,  as 
where  undue  projection,  absolutely  or  relatively,  of  either 
maxilla  exists,  or  where  the  lower  jaw  closes  on  one  side  or 
other  of  the  upper,  will  frequently  compel  a  departure  from  the 
ordinary  arrangement  of  the  artificial  organs,  the  extent  of 
which  must  be  determined  by  the  necessities  of  each  individual 
case. 

In  selecting  teeth  for  a  full  upper  denture  in  those  cases 
where  natural  teeth  are  remaining  below,  or  vice  versa,  the 
color,  size,  and  form  of  the  latter,  w'ill  serve  as  a  guide  in  the 


choice  of  teeth  appropriate  for  the  opposite  jaw.  In  fitting 
and  arranging  the  teeth  ui)on  the  base,  and  in  antagonizing 
them  with  the  opposing  natural  teeth,  the  same  general  prin- 
ciples aj)ply  as  those  already  adverted  to  in  connection  with  full 
upj)er  and  lower  dentures. 

Having  adjusted  the  teeth  to  the  base,  they  should  be  placed 
in  the  mouth,  before  uniting  them  permanently  to  the  plate, 
to  detect  and  remedy  any  error  of  arrangement  either  in  re- 
spect to  prominence,  position,  hiclination,  length,  or  antago- 
nism. 

Forming  a  Rira  to  the  Plate. — If  the  case  is  one  where  sin- 
gle gum  or  block  teeth  are  employed,  and  it  is  intended  to 
form  a  socket  or  groove  upon  the  borders  of  the  plate  lor  the 
reception  of  the  plate  extremities  of  the  teeth,  the  rim  forming 
the  gro<Jve  should  be  fitted  and  soldered  to  the  l)ase  before  in- 


270  MECHANICAL   DENTISTRY. 

vesting  the  piece  in  plaster.  If  the  alveolar  ridge  above  is 
shallow,  and  but  imperfectly  concealed  by  the  lip,  a  rim  to 
the  plate  will  be  inadmissible,  as,  when  the  mouth  is  opened 
and  the  lip  retracted,  as  in  laughing,  the  metallic  band  will  be 
exposed  to  view.  A  rim  may  be  fitted  and  attached  to  the 
base  in  either  of  the  following  ways : 

1.  A  strip  of  plate  from  one  to  two  lines  in  width  is  adjusted 
to  the  plate,  with  one  edge  resting  on  the  uncovered  border  of 
the  plate  close  to  the  gum  extremities  of  the  teeth,  and  the 
other  overlapping  and  embracing  the  latter.  The  rim  may 
consist  of  one  entire  strip  extending  from  heel  to  heel  of  the 
plate,  and  passing  round  the  posterior  molars  to  unite  with 
the  stays;  but  it  may  be  more  conveniently  adjusted  by  em- 
ploying two  pieces,  extending  from  each  heel  of  the  plate,  and 
uniting  in  front. 

2.  A  half-round  wire  with  the  edge  bevelled  where  it  joins 
the  ends  of  the  teeth,  forming  a  narrow  groove,  may,  in  like 
manner,  be  fitted  to  the  plate,  .furnishing  a  shallow  bed  for 
the  gum  extremities  of  the  teeth.  A  narrow  strij)  of  plate, 
about  the  thickness  of  a  heavy  clasp  material,  may  be  sub- 
stituted for  the  half-round  wire.  In  either  case,  the  better 
plan  is  first  to  trace  the  outlines  of  the  gum  portions  of  the 
teeth  upon  the  plate  with  a  sharp  instrument ;  remove  the  wax 
and  teeth  from  the  plate;  draw  another  line  a  little  within  the 
first  all  round,  and  solder  the  rim  to  the  line  last  drawn ;  re- 
move the  teeth  from  the  wax,  and  readjust  the  latter  in  its 
proper  place  upon  the  plate ;  then  fit  each  tooth  separately  to 
the  rim  by  grinding  away  sufficiently  from  the  end  of  the 
tooth  to  effect  an  accurate  adjustment  of  it  to  the  socket.  The 
ends  of  the  teeth  may  be  ground  away  to  the  rim  until  the 
platinum  pins  freely  re-enter  the  rivet-holes  in  the  wax,  thus 
restoring  them  to  their  proper  position  in  relation  to  the  base. 

3.  Another  method  of  forming  a  rim  consists  in  swaging  a 
strip  of  plate  accurately  to  the  form  of  the  parts  to  which  it  is 
applied.  An  impression  in  wax  or  plaster  is  first  taken  of  the 
gum  surfaces  of  the  teeth  and  exposed  border  of  the  plate ;  but 
as  it  will  be  impossible  to  detach  either  wax  or  plaster  in  per- 


ENTIRE    DENTURES.  271 

feet  condition,  when  encircling  the  entire  arch,  or  to  swage 
perfectly  with  a  die  so  unfavorably  formed  for  stamping,  sepa- 
rate impressions  of  the  two  lateral  halves  of  the  piece  should 
be  taken, — from  these  plaster  models ;  and  from  the  latter,  dies 
and  counters; — with  these,  two  strips  of  plate  of  sufficient 
width  are  swaged,  each  extending  from  the  heel  of  the  plate 
to  a  little  beyond  the  median  line  in  front,  overlapping  slightly 
at  the  latter  point.  The  portions  of  the  swaged  strips  embra- 
cing the  plate  ends  of  the  teeth  are  then  trimmed  to  the  proper 
width,  and  scalloped,  if  desired,  in  correspondence  with  the 
festoons  of  the  artificial  gums.  An  upper  denture  rimmed  in 
the  manner  last  described  is  exhibited  in  Fig:.  118.  In  what- 
ever  way  the  rim  is  formed,  when  it  has  been  fitted  to  the  plate 
and  teeth,  it  may  be  held  temporarily  in  place  with  clamps 
adjusted  at  two  or  three  'points  around  the  plate,  and  then 

Fig.  118. 


transferred  to  a  piece  of  charcoal,  and  secured  by  first  tacking 
it  at  two  or  three  points  with  solder.  The  groove  may  then 
be  filled  with  whiting,  mixed  with  water  or  alcohol,  to  pre- 
vent the  solder  from  flowing  in  and  filling  it  up;  after  which 
small  pieces  of  solder  are  placed  along  the  line  of  union  next 
the  edge  of  the  plate,  and  the  rim  permanently  united  through- 
out with  the  blowpipe;  after  which  the  wax  and  teeth  are  re- 
applied to  the  plate. 

(Jondruetincj  and  Attaching  Spiral  Springs. — The  success 
which  has  been  attained  in  the  use  of  atmospheric  pressure 
plates  has  almost  entirely  superseded  the  necessity  of  employ- 
ing spiral  sj)rings  as  a  means  of  support;  nor  should  the  latter 
be  resorted  to  except  under  circumstances  that  preclude  the  use 
of  the  former.  When  api)licd,  they  should  be  attached  to  the 
base  on  each  side  between  the  posterior  bicusj)id  and  first  molar 


272  MECHANICAL    DENTISTEY. 

below,  and  opposite  the  posterior  bicuspid  above.  To  the 
border  of  the  plate  near  the  base  of  the  teeth  a  narrow  strip  of 
plate  is  soldered,  extending  up  and  lying  closely  against  the 
side  of  the  latter — to  the  end  of  which  near  the  grinding  sur- 
faces of  the  teeth  is  adjusted  a  small  circular  cap  of  gold  con- 
nected with  the  standard  by  a  small  wire  on  which  the  looped 
extremity  of  the  spring  plays.     To  each  end  of  the  spring  is 


B 


attached  a  gold  wire,  doubled  iipon  itself  in  such  a  way  as  to 
form  a  loop,  the  closed  ends  being  soldered  together  and  filed 
to  enter  the  hollow  in  the  wire.  A,  Fig.  119.  B,  Fig.  119, 
copied  from  Professor  Harris's  work  on  dental  surgery,  repre- 
sents another  method  of  attaching  springs,  but  the  former  is 
more  readily  constructed  and  will  answer  every  practical  pur- 

FlG.  120. 


pose.     Fig.  120,  exhibits  the  application  of  springs  to  an  upper 
and  lower  denture. 

Investing,  Lining,  Soldering  and  Finishing  the  Plate. — The 
plate,  with  the  wax  and  teeth  in  place,  is  next  encased  in  a 
mixture  of  plaster  preparatory  to  lining  the  teeth  and  uniting 
them  with  solder  to  the  base.     For  this  purpose,  plaster  and 


ENTIRE  DENTURES.  273 

sand  may  be  employed,  using  as  little  of  the  former  as  will 
serve  to  hold  the  investment  together  during  the  subsequent 
manipulations.  Asbestos  may  be  added,  and  is  a  useful  ingre- 
dient. Burnt  plaster,  or  that  which  has  been  previously  used 
for  investing,  may  be  substituted  for  the  sand  and  asbestos, 
adding  a  sufficient  quantity  of  unused  plaster  to  eifect  consoli- 
dation. Either  of  the  combinations  mentioned  will  suffer  but 
little  change  in  the  fire,  if  properly  managed.  It  is  customary 
to  incase  the  piece  in  the  plaster  mixture  to  the  depth  of  from 
one-half  to  three-fourths  of  an  inch,  leaving  only  the  lingual 
surfaces  of  the  plate  and  teeth  uncovered.  However  compara- 
tively free  from  change  of  form  the  best  combinations  of  plaster 
may  be,  yet  some  slight  contraction  of  the  body  of  the  invest- 
ient  doubtless  ensues  on  the  application  of  heat,  and  it  is 
probable  that  so  large  and  resistant  a  mass  must  tend,  in 
some  degree,  to  produce  deformity  of  the  plate  in  soldering ; 
for,  as  the  investient  contracts  and  the  plate  at  the  same  time 
expands  when  heated,  a  change  in  the  form  of  the  latter 
must  occur  whenever  the  force  exerted  by  the  shrinking 
plaster  exceeds  the  expansive  force  of  the  metal ;  and  when 
the  peculiar  form  of  the  upper  plate  is  considered  we  can  read- 
ily conceive  how  a  slight  contraction  of  the  plaster  of  the  thick- 
ness mentioned  may  "  warp  "  or  "  spring  "  the  plate  when  its 
uniform  linear  expansion  and  contraction  is  so  effectively 
opposed.  The  change  in  the  form  of  the  base  from  this  cause 
will,  according  to  the  author's  observations,  be  found,  in  an 
upj)er  plate,  to  exist  on  each  side  of  the  sloping  walls  of  the 
palate,  em1>racing  the  posterior  half  or  two-thirds  of  the  plate 
at  these  two  points, — the  change  manifesting  itself  in  an  in- 
ward displacement  of  the  lateral  walls  of  the  plate  midway 
between  the  summit  of  the  palatal  arch  and  the  most  depending 
])ortion  of  the  ridge.  We  would  suggest  in  explanation  of  this 
result  that,  as  the  ])liister  contracts  with  sufficient  force  to  carry 
the  j)late  with  it,  the  sides  (^f  the  latter  are  approximated,  while 
the  palatal  portion  is,  at  the  same  time  lifted  up.  Now  it 
seems  plain  that  inasmuch  as  the  portions  of  plate  overlapping 

18 


274  MECHANICAL    DENTISTRY. 

the  ridge  is  incased  in  and"  embraced  by  the  plaster,  and  as 
the  palatal  portion  is  arched  in  form  with  its  convexity  pre- 
senting to  the  plaster  and  therefore  self-sustaining  in  respect 
to  its  own  peculiar .  form,  the  special  configuration  of  these 
parts  cannot  suffer  any  appreciable  change ;  but  as  they  are 
forced  toward  the  common  centre  of  the  mass,  their  relation  to 
each  other  is  also  changed,  and  this  changed  relation  must 
necessarily  eventuate  in  a  deformity  of  those  parts  of  the  plate 
which  offer  the  least  resistance  to  the  contractile  force  of  the 
plaster.  In  obedience  to  this  necessity,  the  sides  of  the  plate 
along  the  sloping  walls  of  the  palate,  which  from  their  form 
are  neither  resistant  nor  self-sustaining  under  pressure,  and 
whose  inward  displacement  is  unopposed  by  any  counter-force, 
is  projected  in  toward  the  centre  of  the  palatal  excavation  in 
proportion  as  the  borders  and  central  portions  are  approxi- 
mated ot"  converged  in  the  direction  of  the  centre  of  the  piece. 
The  practical  effect  of  this  approximation  of  the  lateral  and 
posterior  borders,  and  internal  displacement  of  the  plate,  is  to 
make  the  latter  "  bind  "  upon  the  outer  and  posterior  borders 
of  the  alveolar  ridge,  and  to  tlirow  the  central  portion  of  the 
plate  from  the  roof  of  the  mouth.  To  obviate,  as  far  as  prac- 
ticable, any  change  in  the  form  of  the  plate  which  may  result 
from  the  contraction  of  the  plaster  investient,  various  expedi- 
ents have  been  suggested,  but  the  following  will  sufficiently 
counteract  the  influence  of  the  plaster  by  permitting  an  unob- 
structed expansion  and  contraction  of  the  metallic  base.  Take 
a  band  of  tolerably  thick  copper  plate  as  wide  as  the  plate  and 
teeth  are  deep ;  bend  it  to  the  form  of  the  plate,  but  large 
enough  to  leave  a  space  of  nearly  half  an  inch  between  it  and 
the  teeth,  the  ends  being  united  to  each  other  back  of  the  plate 
by  riveting  or  otherwise.  Holes  are  then  made  in  the  band 
at  numerous  points  throughout  its  extent,  through  which  wire 
is  introduced  and  interlaced  on  the  inside  in  such  a  way  as  to 
form  loops,  the  latter  extending  in  to  within  a  short  distance 
of  the  teeth.  The  plaster  is  then  filled  into  the  space  between 
the  band  and  teeth  even  with  the  cutting  and  grinding  surfaces 


ENTIRE   DENTURES.  275 

of  the  latter ;  the  palatal  surface  of  the  plate  is  also  covered 
with  plaster  and  may  be  connected  with  the  outer  portion  by 
a  very  tliin  layer  at  the  edge  of  the  plate,  or  the  two  may  be 
entirely  disconnected.  The  expansion  of  copper  being  very 
nearly  that  of  gold,  the  body  of  the  plaster,  when  heat  is  ap- 
plied, will  be  carried  in  advance  of  the  borders  of  the  plate  as 
the  latter  expands,  while  the  thin  portion  of  plaster  at  the 
edges  of  the  plate  will  allow  the  central  portion  of  the  latter 
to  expand  with  but  little  or  no  interruption.  On  cooling,  the 
entire  mass  will  contract  together  and  assume  its  original  form, 
unless  warping  is  induced  by  other  agencies  acting  indepen- 
dently of  the  enveloping  plaster,  as  excess  or  unequal  distribu- 
tion of  solder,  irregular  heating,  etc. 

It  is  not,  ordinarily,  necessary  to  provide  by  any  special  ex- 
l^edient  against  warping  of  the  lower  plate,  as  any  slight  change 
of  form  consequent  on  contraction  will  not  materially  affect  its 
adaptation  to  the  lower  jaw, — its  only  effect  being  to  impart  to 
the  substitute  a  slight  lateral  play  upon  the  ridge.  The  plaster 
on  the  inside  of  the  lower  piece  may  be  cut  away  to  the  edge 
of  the  plate,  while  that  external  to  the  teeth  should  not  be 
added  in  greater  quantities  than  is  barely  sufficient  to  hold 
the  latter  in  place  whilst  lining  and  soldering  them  to  the 
base. 

The  plate  being  properly  invested,  all  portions  of  the  wax 
attached  to  the  inner  surface  of  the  teeth  and  plate  should  be 
thoroughly  removed  with  suitable  instruments;  after  which 
stays  are  to  be  adjusted  to  the  teeth.  In  reference  to  the 
method  of  forming  and  adjusting  stays,  little  need  be  added  to 
what  has  already  been'  said  when  treating  of  partial  dentures. 
One  method,  not  there  specified,  consists  in  first  fitting  to  each 
tooth  separately,  in  the  usual  manner,  a  thin  stay  formed  of  plati- 
num, which  is  temporarily  fastened  to  the  tooth  by  splitting  and 
spreafling  apart  the  ends  of  the  rivets  with  a  small  chisel-sha])ed 
instrument.  The  teeth  are  then  removed  from  the  investicnt 
and  partially  imbedded  side  by  side  in  plaster,  tlie  i)latinum 
strips  remaining  uncovered.     The  plaster  and  teeth  may  then 


276  MECHANICAL   DENTISTEY. 

be  raised  to  a  full  red  heat  with  a  blowpipe  or  by  placing  them 
in  the  furnace.  Small  pieces  of  gold  plate,  of  equal  fineness 
with  the  base,  are  then  placed  upon  the  surfaces  of  the  platinum 
stays  and  thoroughly  fused  with  the  blowpipe  until  they  flow 
perfectly  in  around  the  rivets,  and  uniformly  over  the  surface 
of  the  linings.  If  sufficient  heat  is  applied,  the  solder  will 
insinuate  itself  between  the  stay  and  tooth,  and  thus  render  the 
coaptation  of  the  two  perfect.  Small  pieces  of  gold  plate  should 
be  added  until  sufficient  thickness  is  imparted  to  the  linings. 
The  backings  are  then  trimmed  smoothly  and  burnished,  when 
they  may  be  placed  back  in  the  investient  in  their  appropriate 
places.  The  linings  which  support  the  teeth  may  be  united  to 
each  other  laterally  in  sections  or  continuously.  When  the 
teeth  are  joined  to  each  other  throughout,  a  very  small  quan- 
tity of  solder  will  be  sufficient  to  support  the  teeth,  provided 
it  is  well  diffused  along  the  joints  uniting  them  perfectly  at  all 
points. 

The  process  of  preparatory  heating,  soldering,  pickling,  and 
finishing  the  plate,  is  the  same  in  all  respects  as  that  described 
when  treating  of  partial  pieces,  and  need  not,  therefore,  be  re- 
capitulated. 

In  the  final  adjustment  of  the  finished  piece  to  the  mouth, 
and  after  any  additional  grinding  of  the  masticating  surfaces  of 
the  teeth  necessary  to  perfect  the  antagonism  has  been  per- 
formed, such  instructions  should  be  given  to  the  patient  in 
regard  to  the  care  and  management  of  the  appliances  as  will 
best  promote  their  immediate  and  successful  use.  The  wearer 
should  be  impressed  with  the  absolute  necessity  of  early  and 
prompt  attention  to  any  injuries  inflicted  upon  the  soft  tissues 
of  the  mouth  by  the  substitutes,  as  much  future  trouble  and 
annoyance,  if  not  permanent  mutilation  of  the  parts,  may  result 
from  neglect,  but  which  may  be  readily  averted,  in  most  in- 
stances, by  a  timely  removal  of  the  sources  of  injury.  To 
obviate,  in  some  measure,  the  tendency  to  displacement  of  the 
base,  which  usually  accompanies  the  first  use  of  artificial  teeth, 
and  especially  the  upper  denture,  the  patient  may  be  directed, 


ENTIRE    DENTURES.  277 

when  dividing  food  with  the  front  teeth,  to  press  the  substance 
back.ward  and  upward  against  the  cutting  edges  of  the  superior 
incisors  at  the  same  time  that  the  opposing  teeth  are  closed 
upon  each  other,  thus  dividing  completely  the  substance  seized. 
In  reference  to  the  mastication  of  food,  it  has  been  sug-o-ested  to 
instruct  the  patient  to  distribute,  by  the  action  of  the  tongue, 
the  portions  of  food  as  equally  as  possible  on  each  side  of  the 
mouth,  in  this  manner  distributing  the  forces  applied,  and 
thereby  lessening  the  chances  of  lateral  displacement  of  the 
substitute. 


278  MECHANICAL   DENTISTRY. 


CHAPTER  XII. 

Porcelain  Teeth — Carved  Block-Teeth. 

PORCELAIN   teeth. 

The  perfection  and  completeness  of  results  attained  at  this 
day  in  the  production  of  porcelain  teeth,  approximating  so 
nearly  the  natural  organs  in  all  their  more  obvious,  physical, 
and  distinctive  characteristics  as  to  be  almost,  if  not  quite,  un- 
distinguishable  from  the  latter  when  applied  in  obedience  to  the 
aesthetic  requirements  of  individual  cases,  is  one  of  the  marvels 
of  ceramic  art.  Nowhere,  perhaps,  have  the  conceptions  of 
genius  been  embodied  in  porcelain  with  more  truthfulness  or 
greater  fidelity  to  nature  than  in  the  exquisite  and  wonderful 
imitations  of  the  dental  manufacturing  laboratory. 

So  amply  and  satisfactorily  has  the  intelligent,  progressive, 
and  well-directed  enterprise  of  manufacturers  provided  for  all 
the  ordinary  needs  of  prosthetic  practice  in  the  almost  endless 
variety  in  size,  color,  configuration,  relation,  and  adaptability 
of  single  and  sectional  teeth,  that  the  work  of  hand-carving  is 
now  rarely  demanded  of  the  general  practitioner  except  in  ex- 
treme cases  resulting  either  from  accident  or  disease.  Thus, 
as  aptly  remarked  by  the  late  Professor  Austen,  "  The  depot 
not  only  renders  service  by  the  superior  excellence  of  the  sur- 
gical instruments  and  prosthetic  materials  which  it  supplies, 
but  it  directly  benefits  the  science  and  art  of  dentistry  by  re- 
leasing the  practitioner  from  manufacturing  toil,  and  giving 
time  for  the  acquirement  of  increased  knowledge  and  skill. 
Thus,  if  the  time  heretofore  given  to  block-making  were  de- 
voted to  the  study  of  dental  aesthetics,  patients  would  have  the 


PORCELAIN   TEETH.  279 

benefit  of  an   artistic  selection  from  a  far  larger  variety  of 
porcelain  dentures  than  could  otherwise  be  possibly  made." 

As  affording  some  curious  as  well  as  practical  information 
in  regard  to  the  composition  and  manufacture  of  porcelain 
teeth,  the  following  descriptions  will  be  found  of  interest: 

Components  of  Dental  Porcelain. — Manufactured  single  and 
sectional  mineral  teeth,  carved  block-teeth,  continuous-gum 
material,  etc.,  are  composed  of  two  distinct  portions, — the 
body  or  base,  and  enamel.  The  chief  mineral  substances 
which  compose  the  body,  are,  silcx,  felsjjar,  and  kaolin.  The 
enamel,  both  crown  and  gum,  consists  principally  o^ felspar. 

The  various  tints  or  shades  of  color  are  imparted  to  the 
porcelain  by  certain  metals  in  a  state  of  minute  division  or 
their  oxides.  The  Jiiore  general  properties  of  the  mineral  in- 
gredients will  be  first  described. 

Sile.r. — Silex,  silica,  or  silicic  acid,  is  a  white  powder,  in- 
odorous, and  insipid.  It  forms  the  chief  part  of  many  familiar 
mineral  formations,  as  quartz,  rock  crystal,  flint,  agate,  calce- 
don,  and  most  sands  and  sandstones,  in  some  of  which  it  occurs 
nearly  pure.  Silica,  in  its  pure  state,  is  insoluble  in  water  or 
acids,  and  is  infusible  in  the  highest  heat  of  the  furnace;  it 
melts,  however,  in  the  flame  of  the  oxyhydrogen  blowpipe, 
passing  into  a  transparent  colorless  glass.  Its  specific  gravity 
is  2.66  ;  and  it  is  composed  of  silicon,  48.04,  and  oxygen,  51.96. 
Only  the  purest  varieties  of  silex  are  employed  in  the  manu- 
facture of  porcelain  teeth.  It  is  prepared  for  use  by  subject- 
ing it  to  a  white  heat  and  then  plunging  it  into  cold  water, 
after  which  it  is  ground  to  a  very  fine  powder  in  a  mortar. 

Felspar. — This  mineral  substance  occurs  crystallized  in  ob- 
lique rhomboidal  prisms,  and  is  a  constant  ingredient  of  gran- 
ite, trachyte,  porphyry,  and  many  of  the  volcanic  rocks.  The 
felspathic  mineral  formations  present  either  a  pearly  or  vitreous 
lustre,  and  vary  in  color,  being  red,  green,  gray,  yellow,  brown, 
flesh-colored,  pure  white,  milky,  transparent,  or  translucent. 
Felspar  yields  no  water  when  calcined ;  melts  at  the  blowpipe 
into  a  white  enamel,  and  is  unaflected  by  acids.    It  is  composed, 


280  MECHANICAL,   DENTISTRY. 

according  to  Rose,  of  silica,  66.75;  alumina,  17.50;  potash, 
12;  lime,  1.25;  oxide  of  iron,  0.75.  It  is  found  in  various 
localities  throughout  the  United  States,  the  purest  and  whitest 
kinds  being  employed  in  the  manufacture  of  mineral  teeth.  It 
is  prepared  for  use  in  the  same  manner  as  silex. 

Felspar,  from  its  ready  fusibility,  serves  to  agglutinate  the 
particles  of  the  more  refractory  ingredients,  silex  and  kaolin ; 
and  when  diffused  throughout  the  mass  imparts  to  the  porce- 
lain a  semi-translucent  appearance. 

Kaolin. — Kaolin,  or  decomposed  felspar,  is  a  fine  white 
variety  of  clay,  and  is  composed  chiefly  of  silica  and  alumina, 
the  latter  being  the  characteristic  ingredient  of  common  clay. 
It  is  found  in  various  localities  throughout  the  Eastern  States, 
and  in  parts  of  Asia  and  Europe.  Kaolin  is  refractory  or 
fireproof,  but  is  rendered  more  or  less  fusible  by  the  contami- 
nations of  iron  and  lime  with  which  it  is  usually  combined. 
The  opaque  and  lifeless  appearance  characteristic  of  the  earlier 
manufacture  of  mineral  teeth  was  due  to  the  introduction  of  a 
relatively  large  proportion  of  this  clay  into  the  body  of  the 
porcelain.  The  peculiar  translucent  and  lifelike  expression 
which  distinguishes  the  beautiful  imitations  of  the  present  day, 
is  due,  in  great  part,  to  the  comparatively  small  proportion  of 
kaolin  clay,  and  an  increased  amount  of  the  more  fusible  and 
vitreous  component,  felspar. 

Kaolin  is  prepared  for  use  by  washing  it  in  clean  water; 
the  coarser  particles  having  settled  to  the  bottom,  the  water 
holding  the  finer  ones  in  solution  is  poured  off,  and  when  the 
suspended  clay  is  deposited  at  the  bottom  of  the  vessel,  the 
water  is  again  poured  oflP,  and  the  remaining  kaolin  dried  in 
the  sun. 

Coloring  Materials. — The  following  metals  and  oxides  are 
employed  in  coloring  mineral  teeth  ;  titanium,  platina  sponge 
and  oxide  of  gold  being  those  chiefly  used  in  producing  the 
more  positive  tints,  and  by  combining  which  in  varying  pro- 
portions, any  desired  shade  of  color  may  be  obtained. 


PORCELAIN    TEETH.  281 


Metals  and  Oxides.  Colors  produced. 

Grold  in  a  state  of  minute  division,    .         .     Rose  red. 
Oxide  of  gold,    .... 
Platina  sponge  and  filings, 
Oxide  of  titanium. 
Purple  of  Cassius, 
Oxide  of  uranium. 
Oxide  of  manganese, . 
Oxide  of  cobalt, 

Oxide  of  silver, .... 
Oxide  of  zinc,    .... 


Bright  rose  red. 
Grayish-blue. 
Bright  yellow. 
Rose  purple. 
Greenish-yellow. 
Purple. 
Bright  blue. 
Lemon  yellow. 
Lemon  yellow. 


As  the  preparation  of  most  of  the  above  colors  requires 
great  care,  and  a  soraewliat  intimate  knowledge  of  chemistry, 
and  as  the  most  delicate  manipulations  are  necessary  to  secure 
accurate  and  satisfactory  results,  it  is  better  for  the  "mechanical 
operator  to  procure  the  coloring  ingredients  already  prepared 
from  some  competent  chemist,  rather  than  attempt  their  pro- 
duction himself.  For  a  particular  description  of  the  various 
modes  of  preparing  them,  the  reader  is  referred  to  Piggot's 
Dental  Chemistry  and  Metallurgy,  and  other  works  treating 
fully  of  the  subject. 

3Iamifaeiure  of  Porcelain  Teeth. — The  subjoined  account  of 
the  processes  concerned  in  the  manufacture  of  porcelain  teeth 
is  descriptive  of  those  at  present  employed  in  the  manufactory 
of  the  late  S.  S.  White,  and  which,  in  the  main,  are  doubtless 
the  same  as  those  of  other  leading  establishments. 

The  felspar  is  first  calained  by  throwing  it  in  large  masses 
into  a  furnace,  and  subjecting  it  to  a  red  heat  and  then  plung- 
ing it  into  water,  which  renders  it  brittle  and  easily  broken  by 
the  hammer  into  small  pieces,  so  that  all  foreign  matters,  such 
as  mica  or  iron,  with  which  it  may  be  mixed,  can  be  separated. 
It  is  then  crushed  between  Hint  .stones,  and  when  fine  enough 
is  afterwards  ground  under  water  in  a  mill  in  which  heavy 
blfx;ks  of  French  burr  stone  revolve  upon  a  nether  millstone 
of  the  same  material,  until  sufficiently  pulverized,  when  it  is 
floated  off  and  aHowed  to  settle.  After  this  the.  water  is  drawn 
off  or  evaporated,  and  the  deposit  of  spar  dried  and  sifted. 

The  silex  is  subjected  to  the  same  treatment. 


282  MECHANICAT.   DENTISTRY. 

The  kaolin,  already  of  the  desired  consistence  as  found  in 
nature,  is  prepared  for  use  by  first  washing  out  impurities,  and 
then  drying. 

The  mineral  ingredients  are  ground  somewhat  coarsely,  but 
the  coloring  materials  are  reduced  to  an  impalpable  powder  by 
means  of  a  mortar  and  pestle  machine  of  great  power. 

When  properly  prepared,  the  several  materials  are  combined 
in  suitable  proportions  to  form  the  body  and  enamels,  and  are 
then  mixed  with  water,  and  worked  into  masses  of  the  required 
consistence  for  moulding.  The  degree  of  plasticity  of  the  body 
and  enamel  pastes  differ  with  the  methods  of  manufacture. 
Formerly,  the  teeth,  when  moulded,  were  first  exposed  to  a 
heat  just  sufficient  to  produce  partial  baking  of  the  body,  and 
this  was  called  cruising  or  biscuiting,  after  which  a  thin  paste 
of  enamel  material  was  applied  with  a  camePs-hair  brush,  and 
the  whole  subjected  to  a  second  heat  for  complete  and  final 
fusion.  This  preliminary  process  of  biscuiting  is  essential  in 
carved  block  and  continuous  gum  work,  but  in  the  S.  S.  White 
factory,  and  probably  others,  this  partial  baking  is  dispensed 
with,  and  the  body  and  enamel  pastes  of  the  uniform  consis- 
tency of  putty  are  introduced  into  the  moulds  in  the  first  in- 
stance, properly  distributed,  and  final  fusion  effected  by  a  single 
exposure  to  heat. 

The  moulds  are  made  of  brass  and  are  in  two  sections, 
one-half  of  the  tooth  being  represented  on  either  side.  The 
exact  form  of  the  tooth  or  teeth  is  carved  out  with  great  care 
and  precision,  and  must  be  anatomically  correct  and  mechani- 
cally perfect,  while  the  matrix,  is  made  about  one-fifth  larger 
than  the  required  size  to  compensate  for  shrinkage  of  the  ma- 
terials in  baking.  Holes  are  drilled  in  each  half  of  the  mould 
to  receive  the  platinum  pins,  and  the  exact  closure  of  the  two 
pieces  of  the  mould  secured  by  guiding  pins. 

The  moulds  having  been  previously  greased,  and  the  plati- 
num pins,  which  vary  in  length  and  thickness  to  meet  special 
requirements,  placed  with  small  tweezers  in  the  holes  provided 
for  them,  the  crown  and  gum  enamels  are  first  carefully  laid 
in  with  small  steel  spatulas  in  the  required  quantity  and  posi- 


PORCELAIN    TEETH.  283 

tion.  The  body  is  then  added,  in  quantity  exceeding  some- 
what the  capacity  of  the  mould,  when  the  sections  of  the 
mould  are  closed  upon  each  other  and  subjected  to  a  pressure 
sufficient  to  insure  compactness  of  the  inclosed  mass.  When 
thoroughly  dried  by  a  shnv  heat,  to  which  the  moulds  are  ex- 
posed, the  teeth  are  readily  disengaged  when  the  matrix  is 
separated,  and  will  be  found  at  this  stage  extremely  friable  and 
tender,  requiring  great  care  in  handling  them. 

They  are  then  sent  from  the  moulding  to  the  trimmer's  room, 
where,  after  critical  inspection,  all  defe(!tive  ones  are  either 
repaired  or  condemned,  all  excess  of  material  filed  smoothly 
away,  and  the  arch  of  the  gum  over  each  tooth  made  true  and 
smooth  with  fine  pointed  instruments.  They  are  then  placed 
on  beds  of  coarse  quartz  sand,  on  fire-clay  trays  or  slides 
ready  for  the  furnace. 

Referring  to  this  stage  in  the  process  of  manufacture,  an  in- 
telligent observer  writes : 

"  Beyond  this,  no  tool  can  follow  them.  Imperfections  here- 
tofore could  be  repaired,  but  in  the  future,  beyond  the  fire,  the 
tooth  is  either  perfect  or  a  failure  irremediable.  The  furnace 
is  an  institution  entitled  to  respect  for  its  intensity.  In  its 
centre  is  a  muffle  of  fire-clay,  entirely  surrounded  by  the  glow- 
ing fuel,  a  charge  of  half  a  ton's  weight  of  coal,  itself  carefully 
bricked  up  before  firing,  that  no  impurities  of  dust  or  vapor 
shall  reach  the  teeth.  Take  out  the  small  half-oval  door  of 
the  muffle  and  you  will  see  an  inner  glow  the  eye  shrinks  from 
registering,  an  incandescence  that  startles  you  by  its  fervor.  In 
from  fifteen  to  thirty  minutes,  teeth  and  fire-clay  slide,  glowing 
like  the  oven,  are  taken  out  done  and  finished.  The  dull 
enamel  has  become  as  glass.  The  lustreless  oxides  have  yielded 
their  color,  and  the  tooth  that  went  in  friable  and  brittle  has 
come  out  adamant.  But  there  is  an  intermediate  skill,  the  ac- 
quisition of  which  is  one  of  the  marvels  of  the  mechanic  arts. 
A  little  too  long  in  that  heat  and  the  teeth  are  ruined,  and  the 
evils  of  'underdone'  are  equally  to  be  guarded  against  as  in 
the  housekeeper's  baking.  It  is  a  trained  judgment,  a  skill  of 
eye  and  handling  that  enables  the  burner  to  lend  success  to  the 


284  MECHANICAL    DENTISTRY. 

work  of  those  who  have  gone  before  him,  and  at  the  precise 
point  where  a  shade  of  failure  is  utter  ruin. 

"  The  teeth  are  now  done  and  ready  for  the  curious,  charac- 
teristic red  wax  cards,  on  which  they  go  to  the  trade." 

We  cannot  close  this  account  of  the  composition  and  manu- 
facture of  porcelain  teeth  more  appropriately  than  by  quoting 
from  an  excellent  popular  treatise,  entitled  The  Teeth,  by  Dr. 
J.  W.  White,  the  present  accomplished  editor  of  the  Dental 
Cosmos : 

"  If  it  is  true  of  any  pursuit,  it  is  emphatically  true  of  the 
attempt  to  imitate  natural  dentures,  that  '  the  beauty  of  the 
result  well  repays  the  highest  exercise  of  art.'  The  manufac- 
turer should  furnish  teeth  in  accordance  with  nature's  types, 
and  each  tooth  in  a  set  should  harmonize  with  the  rest ;  for  though 
each  may  be  an  exact  representation  of  a  natural  tooth,  the 
general  effect  is  spoiled  unless  they  are,  in  all  their  distinguish- 
ing features,  of  the  same  family  or  class  of  teeth.  No  two 
teeth  in  a  natural  set  are  alike ;  every  one  has  its  distinctive 
contour,  and  besides  possessing  individuality,  indicates  the 
character  of  the  adjoining  teeth.  In  an  artificial  set,  unless 
these  distinctive  differences  and  resemblances  have  been  faith- 
fully studied  and  copied,  their  artificial  character  is  apparent. 

"  The  observant  dentist  will  take  into  the  account  complexion* 
age,  sex,  height,  the  color  of  hair  and  eyes,  and  other  charac- 
teristics of  the  individual  when  selecting  teeth  to  replace  lost 
ones ;  and  the  manufacturer  should  be  skilled  in  the  observance 
of  the  varied  classes  of  dentures  required.  To  inattention  in 
this  direction  on  the  part  of  the  dentist,  or  to  dictation  on  the 
part  of  the  patient,  is  to  be  charged  the  unseemly  incongruities 
constantly  staring  the  observer  in  the  face  from  mouths  whose 
lost  organs  have  been  replaced  in  disregard  of  this  universal 
law. 

"No  matter  how  anatomically  correct,  or  how  skilfully 
adapted  for  speech  and  mastication,  an  artificial  denture  may 
be,  yet  if  it  bear  not  the  relation  demanded  by  age,  tempera- 
ment, facial  contour,  etc.,  it  cannot  be  otherwise  than  that  its 
artificiality  will  be  apparent  to  every  beholder. 


PORCELAIN    TEETH.  285 

"This  law  of  correlation,  harmony,  running  through  nature, 
attracts  and  enchants  us  by  an  infinite  diversity  of  manifestations; 
the  failure  to  recognize  its  demands  by  art  is  correspondingly 
abhorrent  to  our  sensibilities. 

"In  the  social  gathering,  a  lady  who  appreciates  the  law  of 
harmony  delights  the  eye  by  the  taste  displayed  in  her  attire ; 
another,  though  more  elaborately  and  expensively  adorned,  yet 
failing  to  harmonize  the  details  of  her  costume,  attracts  atten- 
tion only  by  the  impression  of  incongruity.  We  hear  fre- 
quently from  a  lady  who  is  selecting  a  bonnet,  or  from  a  gen- 
tleman pnrehasing  a  hat  or  other  article  of  wearing  apparel, 
the  question  to  a  friend,  does  this  become  me  ?  the  query 
indicating  the  recognition  that,  however  exquisite  the  material, 
or  excellent  the  manufacture  of  the  article,  a  certain  law  of 
fitness  prevails,  the  failure  to  comply  with  which  makes  the 
wearer  appear  ridiculous.  We  meet  in  the  street  one  the  color 
of  whose  hair  we  expect,  by  the  law  of  association,  to  be  fair, 
or  sandy,  and  if  otherwise,  a  wig  or  a  dye  is  instantly  sug- 
gested. 

"  There  is  a  relation  between  the  physical  form  and  the  voice, 
from  which  we  are  led  to  infer  in  advance  the  character  of  the 
tones  which  from  any  given  individual  may  be  expected, 
^his  law  of  association  in  any  case,  having  led  us  to  anticipate 
a  bass  voice,  the  anomaly,  should  a  falsetto  greet  us,  is  almost 
ludicrous. 

"  There  is  a  similar  relation  between  other  physical  character- 
istics and  the  teeth.  A  broad,  square  face,  or  an  oval ;  a  large, 
coarse-featured  man,  or  a  delicately-organized  woman ;  a  miss 
of  eighteen,  or  a  ra^atron  of  fifty  ;  a  l)runettc  or  a  blonde, — these 
and  other  varieties  present  as  many  diifering  types,  with  teeth, 
in  size,  shape,  color,  density,  etc.,  corresponding.  If,  then,  teeth 
correlated  in  their  characteristics  to  those  which  nature  assigns 
to  one  class,  be  inserted  in  the  mouth  of  one  whose  physical 
organization  demands  a  different  order,  the  effect  cannot  be 
otherwise  than  displeasing  to  the  eye,  whether  the  observer  be 
skilled  in  perf;ej)tion,  or  intuitively  recognizes  inharmony 
without  understanding  the  cause. 


286  MECHANICAL   DENTISTRY. 

"Artificial  teeth  should  be  natural  as  to  shape,  color,  and 
vital  appearance  ;  there  should  be  a  nice  blending  of  the  colors 
of  the  body  and  enamel,  not  an  abrupt  union  of  the  two ;  there 
should  be  the  precise  amount  of  translucency,  and  the  peculiar 
texture  of  the  surface,  and  these  characteristics  should  be  main- 
tained by  artificial  light  as  well  as  by  daylight ;  for  many  teeth 
which  in  daylight  look  reasonably  well  have  a  very  artificial 
appearance  when  exposed  in  the  mouth  to  an  artificial  light. 
They  should  also  possess  strength  sufficient  for  the  uses  for 
which  they  are  designed.  This  strength  should  come  from  the 
quality  of  their  composition,  the  skilful  distribution  of  bulk 
to  parts  most  requiring  it,  and  the  due  form,  position,  and  pro- 
portion of  the  pins,  rather  than  from  any  increase  in  bulk  and 
weight  beyond  that  of  the  natural  organs.  Besides  all  this, 
there  must  be  taken  into  the  account  the  varying  forms  of  the 
jaw  or  maxillary  ridge,  so  that  the  dentist  may  be  enabled  to 
select  teeth  which  are  adapted  to  each  particular  case,  and 
which  can  be  made  to  articulate  nicely  with  each  other  or  with 
the  natural  teeth,  if  there  are  any  remaining  in  the  mouth ; 
otherwise  his  best  efforts  will  not  secure  a  good  appearance, 
comfort  to  the  wearer,  or  usefulness  in  mastication. 

"To  meet  all  these  requirements,  the  reader  can  easily  per- 
ceive, is  no  easy  task,  and  cannot  be  accomplished  without  an 
amount  of  care  and  attention  to  every  detail  which  effectually 
excludes  artificial  teeth  from  the  list  of  cheap  manufactures. 
The  difference  in  all  the  essential  characteristics  which  they 
should  possess,  appears  when  what  are  called  cheap  teeth  are 
compared  with  the  best.  First  upon  the  skill  of  the  manu- 
facturer, and  then  upon  the  judgment  of  the  dentist,  depends 
whether  an  artificial  set  of  teeth  shall  be  pleasing  or  disagree- 
able to  the  observer;  whether  they  shall  disarm  the  suspicion 
of  artificiality,  or  proclaim  it  to  every  beholder. 

"  Those  who  desire  the  result  of  experience,  skill,  and  culture 
in  manufacture  and  application,  who  seek  the  advantages  of 
artistic  taste  and  faithful  service,  should  ponder  the  signifi- 
cance of  the  following  remarks  by  one  who,  in  his  time,  con- 
tributed largely  to  the  development  of  the  art  to  which  he  was 
devoted : 


CARVED    BI.OCK-TEETH.  287 

"'All  works  of  taste  must  bear  a  price  in  proportion  to  the 
skill,  taste,  time,  expense,  and  risk  attending  their  invention  and 
manufacture.  Those  things  called  dear  are,  when  justly  esti- 
mated, the  cheapest ;  they  are  attended  with  much  less  profit 
to  the  artist  than  those  which  everybody  calls  cheap.  Beau- 
tiful forms  and  compositions  are  not  made  by  chance,  nor  can 
they  ever,  in  any  material,  be  made  at  small  expense.  A  com- 
petition for  cheapness,  and  not  for  excellence  of  workmanship, 
is  the  most  frequent  and  certain  cause  of  the  rapid  decay  and 
entire  destruction  in  arts  and  manufactures.'  " 

CARVED    BLOCK-TEETH. 

The  fabrication  of  porcelain  block-teeth  constitutes  a  some- 
what distinctive  branch  of  practical  dentistry,  and  from  the 
delicate  nature  of  the  manipulations  and  long  experience  neces- 
sary to  attain  to  any  considerable  degree  of  excellence  in  the 
various  processes  connected  with  their  manufacture,  their  con- 
struction is  seldom  attempted  by  those  engaged  in  general 
practice.  Cases  occasionally  present  themselves,  however, 
which,  bv  reason  of  unusual  or  unequal  absorption,  or  exten- 
sive and  irregular  loss  of  tissue  as  the  result  of  accident  or 
disease,  demand,  for  their  successful  treatment,  specific  forms 
of  dental  substitutes  not  obtainable  from  any  collection  of 
ready-made  teeth,  single  or  in  sections,  however  large  or  varied. 
To  meet  properly  such  possible  exigencies  of  practice,  either 
the  services  of  an  experienced  block-workman  must  be  ob- 
tained, or  the  demands  of  the  case  must  be  supplied  by  such 
skill  as  the  general  practitioner  can  bring  to  the  work.  To 
the  latter,  the  following  descriptions  of  the  process  may  prove 
helpful. 

A  descri[)tion  of  the  general  properties  of  the  several  in- 
gredients, earthy  and  metallic,  used  in  the  formation  of  block- 
teeth,  has  already  been  given  in  the  preceding  part  of  the 
present  chapter.  The  method  of  compounding  and  preparing 
the  materials  will  next  be  given,  with  various  approved  recipes 
for  body  and  enamel. 

CornponUion  and  Preparation  of  the  Body. — The  porcelain 


288  MECHANICAL   DENTISTEY. 

paste  for  the  body  of  block-teeth  may  be  compounded  from 
either  of  the  following  formulas.  There  are  a  great  variety 
of  recipes,  differing  more  or  less  in  the  proportion  of  the  com- 
ponent ingredients,  but  the  following  will  be  found  to  answer 
every  practical  purpose,  and  are  such  as  are  generally  employai' 
at  this  time  by  experienced  block-workmen. 


NO.  I. 

NO. 

III. 

Delaware  spar, 

12  oz. 

Spar, 

.  12  oz. 

Silex, 

2  oz.  8  dwts. 

Silex, 

.     2  oz.  8  dwts. 

Kaolin, 

11  dwts. 

Kaolin, 

.  12  dwts. 

Titanium, . 

18  to  36  grs. 

Titanium, . 

.  24  grs. 

NO.  II. 

NO, 

.  IV. 

Delaware  spar, 

16  oz. 

Spar, 

.    8oz. 

Silex, 

3Joz. 

Silex, 

.     I5  oz. 

Kaolin, 

J  oz. 

Kaolin, 

.     4  dwts. 

Titanium, . 

20  to  60  grs. 

Titanium, . 

.  22  grs. 

NO. 

V. 

Spar, 

.     2oz, 

Silex, 

.     8  dwts. 

Kaolin,     . 

.    2  dwts. 

Titanium, 

.    4  grs. 

The  titanium  is  first  ground  in  a  mortar  until  reduced  to  an 
impalpable  powder ;  the  silex  is  then  added  and  ground  from 
one  to  three  hours,  or  until  there  is  no  perceptible  grit ;  after 
which  the  kaolin  is  added  and  thoroughly  ground ;  and  lastly 
the  spar,  adding  small  portions  at  a  time,  and  grinding  the 
whole  until  perfect  comminution  and  intermixture  of  the 
several  ingredients  are  effected,  say  from  half  an  hour  to  an 
hour.  The  ingredients  may  be  ground  dry  or  in  water, — in 
the  latter  case  a  sufficient  quantity  of  clean  rain-water  should 
be  added,  from  time  to  time,  to  form  a  mixture  of  about  the 
consistence  of  thick  cream.  After  sufficient  comminution  is 
effected,  the  surplus  water  may  be  abstracted  by  pouring  the 
mixture  upon  a  clean,  dry  slab  of  plaster  of  Paris.  When  it 
acquires  about  the  consistence  of  thick  dough,  it  should  be 
beaten  with  a  wooden  mallet,  or  thrown  repeatedly  and  forcibly 
upon  a  marble  slab,  and,  if  prepared  in  quantities  for  future 
use,  it  should  be  preserved  in  its  plastic  state  by  confining  it 


CARVED   BLOCK-TEETH.  289 

in  a  closely-stopped  earthen  jar.  When  ground  dry,  the 
materials  are  prepared  for  immediate  use  by  adding  to  the 
powder  clean  rain-water  in  sufficient  quantity  to  form  a  thick 
paste ;  it  is  then  well  beaten  on  a  porcelain  or  marble  slab, 
and  pressed,  just  before  using,  between  folds  of  cloth,  to  expel 
perfectly  all  particles  of  air  that  may  be  confined  in  the  body 
of  the  paste. 

Composition  and  Preparation  of  Crown  Enamels. — The 
enamel,  which  forms  the  external  covering  to  the  crowns  of 
porcelain  teeth,  is  composed  wholly  of  felspar,  with  such  color- 
ing matters  as  serve  to  communicate  to  it  the  various  tints  or 
shades  of  complexion  characteristic  of  the  natural  organs.  The 
more  positive  tints,  grayish-blue  and  yellow,  are  produced  by 
titanium,  platinum  sponge,  and  oxide  of  gold;  intermediate 
colors  being  produced  by  varying  the  special  combinations  of 
these  ingredients. 

The  following  recipes  will  furnish  various  tinted  enamels, 
the  varieties  of  grayish-blue  being  applied  to  the  points  or 
coronal  extremities  of  the  teeth — the  yellow  to  the  necks:  the 
two  colors  being  so  blended  when  applied  as  to  run  imper- 
ceptibly into  each  other. 

Grayish-blue  Enamel. 


NO.  I. 

NO.  III. 

Spar* 

.     2  oz. 

Spar,  . 

.     2oz. 

Platina  sponge,    . 

•     ig'-- 

Platina  sponge,  . 

•     f  gr. 

Oxide  of  gold,     . 

•     \  gr- 

Oxide  of  gold,     . 

.     ^gr. 

NO.  II. 

NO.  IV. 

Spar,    . 

.     2oz. 

Spar,  . 

.     2  oz. 

Platina  sponge,    . 

.     ^gr. 

Fli]x,t 

.  24  gr. 

Oxide  of  gold, 

•     I  gr- 

Platina  sponge,  . 

•     i  gr- 

*  The  Boston  spar  is  preferred  on  account  of  its  greater  fusibility. 

t  Flux  is  composed  of  silex,  4  oz. ;  borax,  1  oz. ;  sal  tartar,  1  oz. ;  these 
are  ground  to  an  impalpable  powder  and  packed  in  the  bottom  of  a  clean, 
light-colored  crucible.  A  piece  of  fire-clay  slab  is  then  fitted  into  the  top 
of  the  crucible  and  luted  with  kaolin  clay.  It  is  then  exposed  to  the  heat 
of  a  furnace  until  con)pletely  fused,  when  it  is  removed,  and  when  cold  the 
crucible  is  broken,  all  foreign  particles  or  discolored  portions  thoroughly 
removed,  and  the  remainder  well  pulverized. 

19 


290 


MECHANICAL   DENTISTRY. 


Yellow  L 

Enamel. 

NO.  I. 

NO.  III. 

Spar,      . 

2  oz. 

Spar,     . 

.       2  oz. 

Titanium, 

.     10  grs. 

Titanium, 

,     16  grs 

Platina  sponge, 

*gr. 

Platina  sponge, 

•       igr- 

Oxide  of  gold. 

.       ^gr. 

Oxide  of  gold, 

•       i  gr- 

NO.  II. 

NO.  IV. 

Spar,     . 

.      2oz. 

Spar, 

.     2  oz. 

Titanium, 

.     14  grs. 

Flux,      . 

.     20  grs 

Platina  sponge,      . 

.       2gr. 

Titanium, 

.     10  grs 

Oxide  of  gold, 

.       Jgr. 

In  compounding  enamels  from  the  foregoing  recipes,  the 
coloring  ingredients  should  first  be  ground  to  a  very  fine 
powder,  with  five  or  six  dwts.  of  the  spar;  the  remaining 
portions  of  the  latter  should  then  be  added,  a  little  at  a  time, 
and  ground  for  half  an  hour  or  more.  The  shades  of  color 
may  be  varied  almost  indefinitely  by  changing  the  propor- 
tions of  the  coloring  matter. 

Grayish-Blue  Enamel. 


NO.  I. 

NO.  II. 

Spar, 

.     1  oz. 

Spar, 

.     1  oz. 

Blue  frit,*       . 

.     5  grs. 

Yellow  frit,  f 

.     4  grs 

Gold  mixture,! 

.  20  grs 

Composition  and  Preparation  of  Gum  Enam,els. — Either  of 
the  following  recipes  will  furnish  a  good  gum  enamel,  and 
may  be  used  in  connection  with  any  of  the  compositions  for 
body  heretofore  enumerated. 


NO.  I. 

Gum  frit,  No.  1,  . 
Spar,     . 


NO.  II. 
3  dwts.  Gum  frit,  No.  2,  .     3  dwts. 

9  to  12  dwts.         Spar,.  .         .     3  to  18  dwts. 


*  Blue  frit  is  composed  of  spar,  5^  oz. ;  platina  sponge,  4  dwts. ;  powder 
finely,  make  up  into  a  ball  with  water,  and  fuse  very  slightly  upon  a  slide 
in  a  furnace.  It  is  then  plunged  into  water  while  hot,  and  when  dry,  finely 
pulverized. 

f  Yellow  frit  is  made  by  mixing  intimately  J  oz.  of  spar  with  two  dwts.  of 
titanium,  and  heating  as  above. 

X  Gold  mixture  is  prepared  by  dissolving  8  grs.  of  pure  gold  in  aqua  regia, 
and  then  stirring  in  12^  dwts.  of  very  finely  pulverized  spar.  When  nearly 
dry,  it  is  formed  into  a  ball  fused  upon  a  slide,  and  then  coarsely  pulverized. 


CARVED   BLOCK-TEETH.  291 

It  IS  recommended,  in  order  to  impart  a  granular  appear- 
ance to  the  gum,  to  grind  the  spar  somewhat  coarsely;  any 
required  shade  or  depth  of  gum  color  being  obtained  by  vary- 
ing the  proportions  of  the  frit, — the  latter  containing  the  color- 
ing; ino;redients. 

Gum  frit,  No.  1,  is  composed  of  felspar,  700  grs. ;  flux,  175 
grs. ;  oxide  of  gold,  or  metallic  gold  in  a  state  of  minute  divi- 
sion, 16  grs. 

The  above  are  ground  in  a  mortar  for  five  or  eight  hours, 
or  until  they  are  reduced  to  an  impalpable  powder;  they  are 
then  packed  in  the  bottom  of  a  clean  Hessian  crucible,  coated 
on  the  inside  with  a  thin  mixture  of  pulverized  silex,  and  on 
the  outside  with  kaolin.  A  piece  of  tile  or  slab  is  then  luted 
with  kaolin  to  the  top  of  the  crucible,  when  it  is  placed  in  the 
furnace  for  from  one  to  two  hours,  or  until  complete  vitrifi- 
cation is  effected.  It  is  then  removed,  and  when  cold,  the  crn- 
cible  is  broken  and  all  traces  of  adhering  silex  ground  off;  it 
is  then  broken  in  pieces  and  ground  until  it  will  pass  through 
a  sieve,  No.  9,  bolting  cloth. 

Gum  frit,  No.  2,  is  composed  of  spar,  700  grs. ;  flux,  175 
grs. ;  purple  cassius,  8  grs. 

The  purple  cassius  is  first  thoroughly  ground  in  a  mortar, 
after  which  the  flux  is  added  in  small  quantities  at  a  time, 
then  the  spar  in  the  same  manner,  grinding  until  perfect  com- 
minution and  intermixture  of  the  several  ingredients  are 
effected.  It  is  then  packed  tightly  in  the  bottom  of  a  clean 
white  crucible,  the  inside  lined  with  silex,  and  a  slab  luted  to 
the  top,  as  before,  and  the  whole  exposed  to  a  heat  suflicient  to 
fuse  perfectly.  It  is  then  removed  from  the  fire,  and  when 
cold,  all  foreign  substances  are  ground  off"  and  the  remaining 
portions  pulverized  until  it  will  pass  through  a  sieve  of  No.  9 
bolting  cloth. 

Having  given  the  composition  and  mode  of  preparation  of 
tlie  various  compounds  which  enter  into  the  formation  of  the 
body  and  crown  and  gum  enamels,  it  only  remains  to  describe 
the  different  processes,  concerned  in  the  construction  of  porce- 


292  MECHANICAL  DENTISTRY. 

lain  blocks  from  the  several  compositions  given,  and  first  of 
the  method  of  procuring  an  antagonizing  model. 

Antagonizing  Model  for  an  Entire  Upper  and  Lower  Den- 
ture Constructed  of  Block-teeth. — The  first  step  in  the  process 
of  constructing  block-teeth,  for  either  a  full  upper  set  with  the 
natural  teeth  of  the  opposite  jaw  remaining,  or  for  entire  den- 
tures for  both  jaws,  is  to  secure  an  antagonizing  model."  For 
the  latter,  or  complete  dentures,  above  and  below,  the  method 
does  not  differ  from  that  employed  when  single  gum  teeth  are 
used.  A  rim  of  wax  is  adjusted  to  each  plate  in  the  manner 
heretofore  described,  and  the  plates  placed  in  their  proper  posi- 
tions in  the  mouth  ;  the  wax  drafts  are  then  trimmed  until  the 
exact  fulness  and  contour  of  the  lips  and  cheeks  are  secured  and 
proper  relative  width  is  given  to  the  wax  rims.  Great  exactness 
should  be  observed  in  these  latter  manipulations,  inasmuch  as 
the  wax  drafts  are  the  only  guides  in  the  formation  of  the  blocks, 
both  as  respects  the  form  and  fulness  of  the  arch  and  the 
length  of  the  teeth.  The  proper  relation  of  the  two  pieces  in 
the  mouth  is  now  secured,  the  wax  rims  attached  to  each  other, 
and  the  median  line  of  the  mouth  indicated  on  the  wax,  and 
being  removed  from  the  mouth,  an  antagonizing  model  pro- 
cured in  the  same  manner  as  described  in  a  former  chapter. 

Antagonizing  Model  for  an  Entire  Upper  Denture  with  the 
Natural  Teeth  of  the  Opposing  Jaw  Remaining. — A  rim  of  wax, 
half  an  inch  or  more  in  width,  is  attached  to  the  ridge  of  the 
plate  and  the  latter  placed  in  the  mouth.  The  patient  is  then 
directed  to  close  the  jaws  until  the  cutting  edges  and  grinding 
surfaces  of  the  teeth  of  the  opposing  jaw  are  fairly  imbedded 
in  the  wax.  The  piece  is  then  removed  from  the  mouth  and 
the  wax  rim  detached  from  the  plate  by  holding  the  latter  for 
a  moment  over  a  spirit-flame.  The  wax  is  then  placed  upon 
a  strip  of  paper  with  the  side  indented  by  the  teeth  looking 
upward,  the  surface  of  the  wax  oiled  and  a  batter  of  plaster 
poured  upon  it,  filling  the  imprints  of  the  teeth  and  running 
back  an  inch  and  a  half  or  more  behind  the  wax,  raising 
the  plaster  to  a  level  of  half  an  inch  above  the  wax.  When 
the  plaster  is  sufficiently  condensed,  it  is  turned  over,  the  wax 


CARVED    BLOCK-TEETH. 


293 


removed  without  fracturing  the  plaster  teeth,  and  a  crucial 
groove  made  in  the  surface  of  the  model  posterior  to  the  teeth. 
This  constitutes  the  lower  section  of  the  antagonizing  model, 
and  is  a  representation  of  the  teeth  of  the  lower  jaw.  The 
upper  section  is  next  obtained  in  the  following  manner :  A 
second  rim  of  wax,  in  width  equal  to  the  required  length  of 
the  teeth,  is  adjusted  to  the  plate  as  before  and  placed  in  the 
mouth.  The  exact  contour  and  fulness  of  the  arch  required 
is  then  given  to  the  external  or  labial  surface  of  the  wax  draft, 
and  the  lower  edge  cut  away  until  the  required  approximation 


of  the  jaws  is  secured,  and  the  points  of  all  the  teeth  remaining 
below  touch  the  wax  at  the  same  instant.  The  patient  is  now 
required  to  close  the  jaws  gently  upon  each  other  until  a  slight 
indentation  is  made  in  the  Avax  by  the  opposing  teeth  ;  the 
median  line  of  the  mouth  is  then  marked  upon  the  wax  and 
the  plate  removed.  The  plate  and  wax  are  now  adjusted  to 
the  lower  section  of  the  model,  the  points  of  the  plaster  teeth 
being  received  into  the  indentations  in  the  wax  made  by  the 
natural  teeth.  The  upper  and  posterior  surface  of  the  lower 
section  of  the  model  having  been  varnished  and  oiled,  and  the 


294 


MECHANICAL,   DENTISTRY. 


exposed  surface  of  the  plate  also  oiled,  a  mixture  of  plaster  is 
poured  in  upon  the  latter  and  back  upon  the  model,  raising 
the  whole  to  a  level  of  half  an  inch  above  the  plate.  The  two 
sections,  when  the  latter  portion  of  plaster  has  consolidated, 
are  then  separated,  reserving  the  lower  part  of  the  antagonizing 
model  for  future  use. 

Forming  a  Matrix  for  Moulding  the  Body  Preparatory  to 
Carving  the  Teeth. — As  the  process  of  forming  a  matrix  in 
which  to  mould  the  porcelain  paste,  giving  the  general  form  and 


Fig.  122. 


outlines  to  the  blocks  before  carving  the  teeth,  is  the  same 
for  an  upper  and  lower  denture,  it  will  be  sufficient  to  describe 
the  method  as  it  relates  to  the  superior  arch.  A  matrix  for 
an  entire  denture  above  or  below,  whether  consisting  of  three, 
four,  or  six  blocks,  is  ordinarily  made  to  consist  of  three  dis- 
tinct pieces  independently  of  the  plate  and  model,  and  is  con- 
structed in  the  following  manner  :  Three  conical  shaped  holes 
are  made  in  the  sides  of  the  model,  one  in  front  and  one  on 
each  side,  to  furnish  a  fixed  articulation  for  the  three  sections 


CARVED    BLOCK-TEETH. 


295 


forming  the  external  walls  of  the  matrix.  The  appearance  of 
the  model  when  thus  prepared  with  the  plate  and  wax  run  m 
place  is  exhibited  in  Fig.  121.  The  sides  of  the  model  and 
external  face  of  the  wax  are  now  oiled,  and  both  surfaces 
covered  with  a  batter  of  plaster  to  the  depth  of  a  fourth  or  a 
half  of  an  inch,  extending  from  the  base  of  the  model  to  the 
lower  edge  of  the  wax,  and  posteriorly  about  half  way  on  each 
side  of  the  model  to  form  a  matrix  for  the  front  block,  "or  the 


two  anterior  bl(»cks,  if  the  arch  is  made  to  consist  of  more  than 
three  sections.  Supposing  the  wax  removed  from  the  plate 
and  this  front  piece  in  place,  the  several  parts  will  j)resent  the 
apiiearance  shown  in  Fig.  122.  The  plaster  rim  forming  the 
external  wall  of  the  front  block  being  removed,  plaster  is  again 
adde^l,  as  before,  to  the  outer  surfaces  of  the  model  and  wax, 
extending  it  from  the  heel  of  the  idate  on  each  side  forward  an 
eighth  or  a  fourth  of  an  inch  in  advance  of  the  posterior  ex- 
tremities of  the  plaster  rim  first  formed.  Wiicn  hard  the 
plaster  is  trimmed  even  with  the  edge  of  the  wax  draft,  and 
the  two  pieces  removed  from  the  model.     The  matrices  ibrmed 


296  MECHANICAL   DENTISTEY. 

by  these  lateral  sections  when  readjusted  to  the  model  with  the 
wax  removed  are  shown  in  Fig.  123.  Having  thus  provided 
a  matrix  determining  the  general  outline  and  length  of  the 
teeth  for  the  entire  arch,  the  wax  draft  is  removed  and  the 
plate  thoroughly  cleansed  preparatory  to  moulding  the  paste, — 
before  doing  which,  however,  the  line  upon  the  wax  indicating 
the  median  point  of  the  mouth  should  be  extended  across  the 
model' 

Moulding  the  Porcelain  Paste  Preparatory  to  Carving  the 
Teeth. — In  the  process  of  constructing  an  entire  denture,  it  is 
impracticable,  owing  to  the  shrinkage  of  the  body,  to  form  a 
single  continuous  block  or  full  arch  without  materially  chang- 
ing its  relation  and  adaptation  to  the  metallic  base,  and  also  to 
the  natural  organs  in  cases  where  the  latter  are  remaining  in 
the  opposite  jaw ;  hence  it  is  customary,  as  before  intimated, 
to  divide  the  arch  into  sections, — usually  three;  a  central  front 
block  embracing  the  incisors  and  cuspidati,  and  two  lateral 
blocks  including  the  bicuspids  and  molars  on  each  side ;  or  the 
denture  may  consist  of  four  blocks,  dividing  the  arch  between  the 
central  incisors,  and  also  between  the  first  and  second  bicuspids 
on  each  side ;  making  the  two  anterior  blocks  to  consist  each  of  a 
central  and  lateral  incisor,  a  cuspidatus,  and  anterior  bicuspid, 
and  the  posterior  blocks  of  the  second  bicuspid  and  the  two 
molars.  Again,  the  arch  is  sometimes  divided  into  six  blocks, 
— an  anterior  embracing  the  central  and  lateral  incisor  and 
cuspidatus,  a  central  comprising  the  bicuspids,  and  a  p6sterior 
including  the  molars.  If  constructed  in  three  sections,  as  is 
ordinarily  the  case,  the  front  block  should  be  moulded  and 
carved  first.  The  material  for  the  body,  if  in  a  dry  state,  is 
mixed  with  a  sufficient  quantity  of  clean  rain-water  to  form  a 
thick  batter,  and  mixed  thoroughly  in  a  mortar.  It  should 
then  be  poured  upon  a  dry  slab  of  plaster  of  Paris,  and  when  the 
excess  of  water  is  absorbed,  removed,  and  well  beaten  with  a 
spatula  on  a  marble  or  porcelain  slab  until  it  assumes  a  some- 
w^hat  pasty  form ;  it  may  then  be  well  pressed  between  folds  of 
cloth  to  force  out  any  remaining  portions  of  confined  air.  The 
plaster  rim  forming  the  matrix  for  the  front  block  is  now  ad- 


CARVED    BLOCK-TEETH,  297 

justed  in  its  proper  position  to  the  model,  and  its  inner  surface, 
as  well  as  that  of  the  plate,  oiled;  the  porcelain  paste  is  then 
packed  into  the  matrix  as  compactly  as  possible,  filling  it  even 
with  the  upper  edge  of  the  plaster  rim.  When  the  paste  has 
been  worked  in  as  solidly  as  possible,  patting  it  with  the  fin- 
gers or  suitably  formed  instruments  as  successive  portions  are 
added,  it  should  be  trimmed  even  with  the  edge  of  the  plaster 
rim  and  the  palatal  surface  cut  away  to  near  the  thickness  re- 
quired for  the  teeth  included  in  the  block,  leaving  it  somewhat 
thicker,  however,  to  compensate  for  the  shrinkage  of  the  body, 
and  to  allow  for  small  portions  which  will  be  cut  away  in 
carving  the  teeth.  The  plaster  rim  forming  the  external  bor- 
der of  the  matrix  is  now  loosened  by  tapping  gently  upon  the 
model  and  then  carefully  removed.  The  mark  upon  the 
model,  showing  the  mesial  line  of  the  mouth  and  indicating 
the  proper  position  of  the  central  incisors,  is  then  extended 
across  the  block,  after  which  the  width  of  each  adjoining  tooth 
is  lined  off,  making  each  one  as  much  broader  than  will  be  re- 
quired in  the  finished  piece  as  the  porcelain  composition  will 
shrink  in  baking, — this,  in  a  block  embracing  the  six  anterior 
teeth,  will  be  equivalent  to  about  one-third  or  one-half  the 
width  of  a  bicuspid  on  each  side.  If  the  case  is  one  requiring 
a  full  denture  above  and  below,  the  operator  should  next  pro- 
ceed to  mould  the  front  block  for  the  lower  arch  in  the  same 
manner  as  described  for  the  upper.  The  two  sections  of  the 
antagonizing  model  are  then  placed  together,  and  the  proper 
relative  width  for  the  lower  teeth  indicated  upon  the  inferior 
block, — the  drawn  lines  upon  the  upper  block  serving  as  a 
guide.  Tlie  points  to  which  the  posterior  extremities  of  the 
front  block  extend  on  each  side  of  the  ))late  should  be  marked 
upon  corresponding  points  of  the  model  above  and  below,  to 
enable  the  manipulator  to  determine  how  far  the  side  blocks 
should  be  extended  anteriorly  when  moulding  the  paste  for  the 
latter, — the  marks  upon  the  model  being  subsequently  trans- 
ferred to  the  lower  edges  of  the  lateral  sections  of  plaster  con- 
cerned in  the  formation  of  the  side  matrices.  Before  njmoving 
the  front  blocks  from  the  plates  preparatory  to  carving  the 


298  MECHANICAL   DENTISTRY, 

teeth,  the  surface  of  the  paste  may  be  dried  somewhat  by 
throwing  upon  it,  with  a  blowpipe,  a  broad  spreading  flame 
from  a  spirit-lamp.  The  blocks  are  then  carefully  detached 
by  rapping  lightly  upon  the  model,  assisted  by  gentle  traction 
with  the  fingers.  The  front  blocks  being  removed  from  the 
upper  and  lower  plates,  the  side  sections  of  plaster  concerned 
in  the  formation  of  the  posterior  matrices  are  adjusted  to  the 
model,  and,  being  oiled,  the  paste  filled  in  as  before  described, 
extending  each  block  forward  beyond  the  point  occupied  by 
the  cuspidatus  of  the  front  block  a  distance  equal  to  about  one- 
third  or  one-half  of  the  width  of  the  latter.  These  are  then 
cut  away  even  with  the  edges  of  the  plaster  rims  and  trimmed 
on  the  palatal  sides,  leaving  them  somewhat  thicker  than  will 
be  required  for  the  bicuspids  and  molars.  The  plaster  walls 
of  the  matrices  are  then  removed  ;  the  two  parts  of  the  articu- 
lating model  placed  together,  and  the  relative  width  and  posi- 
tion assigned  to  the  upper  and  lower  teeth  by  drawing  lines 
across  the  external  surface  of  the  blocks.  They  are  then  sepa- 
rately removed  from  the  plates  in  the  manner  before  described, 
and  the  necessary  additional  portions  of  paste  added  to  the 
grinding  surfaces  to  compensate  for  the  contraction  of  the  body 
in  baking.  In  constructing  a  full  upper  denture  with  all  or  a 
portion  of  the  natural  organs  remaining  below,  the  proper 
width  to  be  given  to  the  upper  teeth,  as  well,  also,  as  the  re- 
quired relation  or  antagonism  of  the  artificial  with  the  oppos- 
ing natural  teeth,  may  be  readily  determined  by  applying  the 
lower  portions  of  the  antagonizing  model  representing  the 
teeth  of  the  under  jaw,  and  marking  upon  each  block,  as  it  is 
being  moulded,  the  necessary  width  and  position  of  each  tooth 
above, — being  careful  to  make  allowance  for  shrinkage  by 
adding  to  the  length,  width  and  thickness  of  each  block  as 
much  as  will  compensate  for  the  contraction  of  the  body.  In 
every  other  particular,  the  process  is  conducted  in  the  same 
manner  as  heretofore  described. 

Carving  the  Teeth. — The  teeth  are  first  separated  by  drawing 
between  them  a  thread  attached  to  a  small  bow,  and  it  may  be 
observed  in  this  connection  that  the  most  careful  and  delicate 


CARVED    BLOCK-TEETH.  299 

manipulation  is  required  in  handling  the  blocks  while  carving 
to  prevent  portions  of  the  paste  from  crumbling  away,  a  ten- 
dency that  may  be  counteracted,  in  some  measure,  by  moisten- 
ing the  paste  occasionally  with  a  little  water  taken  up  on  the 
point  of  the  carving  knife.  The  general  outline  of  each  tooth 
having  been  traced  upon  the  exterior  surface  of  the  block  with 
the  point  of  the  instrument,  the  operator  proceeds  next  to  give 
the  distinct  and  characteristic  form  to  the  crowns,  and  the  har- 
monious and  agreeable  effects  produced  will  depend  upon  the 
fidelity  with  which  the  manipulator  copies  nature  in  the  form 
and  arrangement  of  the  teeth.  The  requirements  of  individual 
cases  are  too  varied  in  their  nature  to  admit  of  specific  direc- 
tions in  respect  to  their  formation, — a  careful  study  of  the 
modified  forms  of  the  natural  organs,  combined  with  some  de- 
gree of  manipulative  tact,  will  enable  any  one,  after  sufficient 
experience,  to  attain  to  satisfactory  results  in  this  particular. 


After  the  teeth  are  I'ormcd,  and  the  body  of  the  block  is  re- 
duced to  the  required  thickness,  superfluous  portions  extending 
from  the  ends  of  the  block  should  be  cut  away,  leaving  enough, 
however,  projecting  to  allow  for  grinding  when  jointing  and 
adjusting  the  several  blocks  to  the  metallic  base.  Fig.  124 
exhibits  the  general  form  of  the  blocks  when  carved,  showing 
also  the  platinum  pins,  but  which  are  not  usually  attached  to 
the  blocks  until  after  the  latter  are  first  biscuited. 

Q-uoinfj,  or  Bbieaitiny — The  blocks  being  carved,  are  next 
placed  on  a  fire-clay  slab  with  their  palatal  surfaces  resting  on 
a  bed  of  silex.  As  soon  as  the  paste  has  become  thoroughly 
dry,  the  slab  may  be  gradually  introduced  into  the  muffle  of  a 
baking  furnace  (Fig.  15),  and  exposed  to  a  full  red  heat  until 
semi-fusion  of  the  body  takes  place.  This  partial  vitrification 
of  the  body  serves  to  agglutinate  the  particles  of  the  compound, 


300  MECHANICAL   DENTISTRY. 

and  is  termed  Gruoing  or  biscuiting.  When  removed  from  the 
furnace,  and  cool,  the  platina  pins  should  be  introduced  into 
the  blocks  before  applying  the  gum  and  crown  enamels,  and 
is  accomplished  in  the  following  manner.  One  or  two  small 
holes,  as  the  case  may  require,  are  drilled  into  the  body  of  the 
blorik  immediately  behind  and  below  the  crown  of  each  tooth, 
extending  about  half  way  through  the  block  ;  into  these,  plati- 
num pins  or  wires  are  introduced,  a  head  being  formed  to  the 
end  of  the  pin  entering  the  block.  A  small  portion  of  the 
body  composition,  mixed  with  water  to  the  consistence  of  thin 
cream,  is  then  worked  into  the  hole  around  the  pin  with  a 
sharp-pointed  carving  knife  or  camel's-hair  brush,  its  intro- 
duction being  facilitated  by  first  immersing  the  block  in  water 
immediately  before  inserting  the  ]>ins. 

AppliGation  of  the  Crown  and  Gum  Enamels. — The  gum 
enamel  is  applied  first,  the  material  being  first  prepared  by 
mixing  the  gum  composition  with  sufficient  clean  rain-water 
to  form  a  batter  of  about  the  consistence  of  thin  cream.  This 
is  then  taken  up  with  a  camel's-hair  brush  and  applied  uni- 
formly to  all  parts  of  the  external  surface  of  the  block  repre- 
senting the  natural  gum.  It  should  be  applied  very  carefully 
to  the  necks  of  the  teeth,  forming  a  neat  and  well-defined  fes- 
toon at  these  points.  In  applying  the  crown  enamel  to  the 
labial  surfaces  of  the  teeth,  it  is  customary,  in  imitation  of  the 
natural  organs,  to  so  distribute  the  more  positive  tints  as  to 
give  to  that  portion  of  the  crown  representing  the  neck  of  the 
tooth  a  somewhat  yellowish  hue,  and  to  the  points,  a  grayish-blue 
tint.  To  effect  this,  the  material  for  the  yellow  enamel,  re- 
duced to  the  consistence  before  mentioned,  is  first  applied  to 
the  necks,  uniting  it  carefully  with  the  gum  enamel ;  and  after- 
wards the  grayish-blue  to  the  points,  extending  it  a  little  be- 
low the  cutting  edges  of  the  incisors,  and  the  cusps  of  the 
cuspidati,  bicuspids,  and  molars,  giving  to  the  teeth,  at  these 
points,  a  translucent  appearance.  It  is  only  the  external  and 
lateral  surfaces  of  the  teeth  that  are  enamelled,  the  palatal 
surfaces  remaining  unglazed.     The  yellow  and  blue  enamels 


CARVED   BLOCK-TEETH.  301 

should  be  so  blended  when  applying  them  to  the  crowns  that 
the  one  shall  fade  away  imperceptibly  into  the  other. 

Final  Baking. — The  enamelling  completed,  the  blocks  are 
placed  upon  a  bed  of  silex  on  a  slide,  and  the  latter  carefully 
and  slowly  introduced  into  the  mouth  of  the  furnace.  The 
fire  should  then  be  urged  to  a  clear  white  heat,  and  when  per- 
fectly dry,  the  blocks  should  be  carried  with  the  slide  into 
the  body  of  the  muffle,  and  the  mouth  of  the  latter  closed 
tightly  with  a  fire-clay  plug.  Some  knowledge  of  the  requi- 
site degree  of  heat  and  time  necessary  to  effect  perfect  fusion 
of  the  ingredients  composing  the  blocks  is  required,  and  these 
are  ordinarily  well  known  to  experienced  block-workmen,  but 
those  unaccustomed  to  the  process  will  better  determine  the 
completion  of  the  baking  by  introducing  into  the  muffle  along 
with  the  blocks  a  small  portion  of  the  body  covered  with 
enamel  attached  to  one  end  of  a  platinum  wire,  the  other  pass- 
ing through  a  small  stopper  fitted  to  the  centre  of  the  plug 
closing  the  end  of  the  muffle,  and  which  may  be  removed  and 
the  wire  withdrawn  from  time  to  time  to  observe  the  effect  of 
the  heat  upon  the  test-piece.  When  this  is  seen  to  be  per- 
fectly fused,  as  evidenced  by  a  uniform  glossiness  of  the  sur- 
face, the  slab  should  be  drawn  to  the  mouth  of  the  muffle,  the 
draft  cut  off,  and  the  blocks  allowed  to  cool  gradually  with  the 
furnace.  In  place  of  using  a  test-piece,  however,  it  will  an- 
swer the  purpose  to  withdraw  the  slide  to  the  mouth  of  the 
muffle  occasionally,  where  it  may  be  readily  inspected  and  the 
progress  of  baking  noted.  When  sufficiently  cool  to  be  taken 
in  the  hand,  the  blocks  are  removed  from  the  furnace. 

Fitting  and  Attaching  the  Blocks  to  the  Metallic  Base. — On 
applying  the  blocks  to  the  plate,  it  will  be  found  that  a  greater 
or  less  change  of  relation  between  the  two  has  occurred  in  the 
process  of  baking,  so  that  the  base  of  the  former  will  not  fit 
the  portion  of  the  plate  on  which  they  rest  as  accurately  as  when 
first  moulded.  It  will,  therefore,  be  necessary,  when  adjusting 
each  block,  to  grind  away  somewhat  from  the  base  of  the  latter 
until  the  coaptation  of  the  two  surfaces  is  as  perfect  as  practi- 
cable.    The  «('V(;rul  blocks  should  also  at  the  same  time  be 


302  MECHANICAL   DENTISTRY. 

accurately  united  to  each  other  laterally,  grinding  away  from 
the  ends,  and  approximating  the  sections  as  the  articulation  of 
the  opposing  dentures  may  require  to  eifect  a  proper  and  efficient 
antagonism,  and  which  may  be  determined  by  the  use  of  the 
antagonizing  model  employed  in  moulding  the  blocks.  After 
the  blocks  are  fitted,  and  the  teeth  antagonized,  and  before  unit- 
ing the  former  permanently  to  the  plate,  a  rim  should  be  formed 
and  attached  to  the  borders  of  the  metallic  base  to  form  a  socket 
for  the  plate  extremities  of  the  blocks,  and  which,  extending 
around  the  margins  of  the  plate,  should  be  continued  across  the 
heel  of  the  latter  on  each  side  and  made  continuous  with  the 
band  of  lining  on  the  palatal  sides  of  the  teeth.  The  manner 
of  forming  and  attaching  the  rim  does  not  differ  from  the  method 
heretofore  described  in  connection  with  full  dentures  constructed 
of  single  gum  teeth,  and  to  which  the  reader  is  referred.  The 
rim  fitted,  and  the  blocks  replaced,  the  whole  is  invested  in  the 
usual  way,  the  wax  removed  from  the  plate,  and  a  continuous 
band  or  lining  adjusted  to  each  block.  The  latter  is  accom- 
plished by  first  cutting  a  pattern  of  the  band  from  sheet  lead 
of  the  length  of  the  block,  and  of  the  required  width,  trimming 
the  edge  applied  to  the  plate  in  such  a  manner  that  when  ad- 
justed to  the  backs  of  the  teeth  it  will  lie  in  uniform  contact 
with  the  base;  this  is  then  pressed  against  the  pins  with  suffi- 
cient force  to  perforate  it.  The  lead  pattern  is  then  placed  upon 
a  strip  of  gold  of  the  required  thickness,  and  the  counterpart 
of  the  pattern  cut  from  the  gold  plate,  marking  at  the  same 
time  the  points  to  be  perforated  for  the  platinum  rivets.  This 
is  then  pierced  with  a  plate-punch,  and  the  strip  bent  to  the 
proper  curve  and  applied  to  the  block,  when  it  is  bound  to  the 
latter  by  splitting  and  spreading  apart  the  ends  of  the  rivets. 
A  band  is  thus  applied  to  each  block.  Solder  is  then  applied 
along  the  joints,  and  over  the  pins,  and  all  parts  united  with 
the  blowpipe  in  the  usual  manner.  The  piece  is  then  finished 
up  the  same  as  ordinary  gold  Avork.  Fig.  125,  exhibits  a 
palatal  view  of  an  upper  set  of  block- teeth  mounted  on  a  metallic 
base.  When  skilfully  executed,  the  finished  work  presents  a 
beautiful  and  highly  artistic  appearance.     The  application  of 


CARVED    BLOCK-TEETH. 


303 


sectional  porcelain  blocks  to  the  necessities  of  mechanical  prac- 
tice has  been  greatly  extended  in  connection  with  the  vulcan- 
ite and  celluloid  bases,  and,  to  a  limited  extent,  with  other 
processes.  Their  construction,  however,  is  modified  some- 
what by  the  requirements  of  these  special  processes,  and  as 
made  for  the  latter  are  of  such  approved  manufacture,  and 
are  supplied  in  such  abundance  and  at  so  reasonable  a  cost 
by  all  the  principal  dental  furnishing  establishments,  that 
the  general  practitioner,  we  apprehend,  will  ordinarily  find  it 
more  convenient  and  economical  to  purchase  rather  than  manu- 
facture them  himself. 

Fig.  125. 


The  subjoined  account,  descriptive  of  a  new  method  of  making 
block-teeth,  by  Dr.  William  Calvert,  Avas  inadvertently  omitted 
in  the  former  edition  of  this  work.  The  process  has  received 
marked  commendation  by  competent  persons  who  have  investi- 
gated its  merits,  and  will  be  highly  esteemed  by  those  who 
desire  to  excel  in  this  beautiful  but  difficult  art. 

"  The  first  pre})aratory  step  to  be  taken,  after  having  correct 
articulating  models,  is  to  select  single  teeth  so  defined  as  may 
eithersuit  the  taste  of  the  operator  or  the  peculiarity  of  the  case, 
and  supposing  the  case  to  be  an  upper  denture,  it  will  be  neces- 
sary to  have  hvo  front  and  two  lateral  incisors,  two  canine  or 
cuspids,  two  bicuspids  (or  if  more  convenient  the  cuspids),  and 
four  molars,  all  of  which  should  be  sufficiently  large  to  com- 
pensate for  shrinkage,  in  the  material  of  which  the  teeth  are  to 
be  corn[)Osed. 

"  The  plate  upon  which  the  blocks  arc  to  be  made,  and  to 


304  MECHANICAL   DENTISTRY. 

which  they  are  to  be  subsequently  fitted,  being  upon  its  cor- 
responding model,  a  rim  of  wax  may  be  placed  upon  it,  and 
the  teeth  arranged  upon  the  wax,  articulating  with  the  antago- 
nizing model,  allowing  sufficient  in  the  length  of  the  teeth  for 
shrinkage.  Beginning  with  the  front  incisors,  the  teeth  should 
be  set  to  the  wax  (as  above)  as  far  back  on  each  side  as  the 
first  bicuspids,  inclusive;  then  leaving  a  space  equal  to  the 
width  of  half  a  tooth,  the  arch  may  be  completed  by  the  addi- 
tion of  the  molars,  two  on  each  side.  The  teeth  having  been 
thus  arranged  upon  the  wax,  with  reference  to  regularity  or 
irregularity,  height,  etc.,  the  desired  outline  of  gum  may  be 
filled  up  with  wax. 

"  Special  care  is  requisite  in  so  trimming  the  wax  where 
joints  are  contemplated,  that  no  subsequent  alteration  will  be 
needed  during  the  further  manipulations. 

"  It  will  be  necessary,  previous  to  making  the  moulds,  to 
make  some  provision  for  replacing  them,  after  they  have  been 
once  removed,  so  that  they  shall  occupy  the  same  position  as 
they  did  previous  to  their  first  removal.  For  this,  it  will  be 
only  necessary  to  make  some  conical  holes  in  the  face  of  the 
cast,  say  two  on  each  side,  between  the  centre  and  the  first  bi- 
cuspid teeth,  and  two  opposite  the  molar  teeth  of  each  side. 
These  holes  need  not  be  more  than  about  a  quarter  of  an  inch 
deep,  and  should  be  but  a  short  distance  below  the  edge  or 
line  of  the  plate.  The  face  of  the  cast,  including  said  holes, 
should  now  be  varnished,  when  the  case  is  ready  for  making 
the  moulds. 

"  The  first  mould  to  be  made  should  be  that  including  the 
four  incisors,  two  canine,  and  two  first  bicuspids,  eight  teeth 
in  all.  This  may  be  done  by  simply  oiling  the  face  of  the 
teeth,  outline  of  gum,  and  plaster  cast,  and  pouring  plaster  of 
Paris  of  a  proper  consistency  over  the  surface  of  the  same, 
allowing  it  to  fall  slightly  over  the  cutting  edges,  so  as  to  form 
a  more  perfect  mould.  This  mould  should  be  divided  in  the 
centre,  making  two  sections,  which  can  be  done  by  cutting 
through  the  plaster  while  in  the  state  of  hardening ;  or,  what 
is  perhaps  better,  before  applying  the  plaster,  make  an  incision 


CAEVED    BLOCK-TEETH.  305 

in  the  wax  outline  of  gum,  in  which  place  a  thin  slip  of  sheet 
lead,  letting  it  extend  a  little  above  the  cutting  edges  of  the 
teeth,  and  as  far  down  the  face  of  the  cast  as  is  desired  to  ex- 
tend the  mould.  When  hard,  remove  from  the  cast  and  teeth, 
and  we  have  the  untrimmed  mould  for  said  eight  teeth.  Pre- 
vious to  making  the  moulds  for  the  back  teeth,  it  is  necessary 
to  remove  the  first  bicuspids,  or  the  cuspids  representing  them, 
from  the  position  they  occupied  in  making  the  mould  just  de- 
scribed, and  placing  them  beside  the  first  molars  so  as  to 
represent  the  second  bicuspids.  Care  is  to  be  taken  in  re- 
moving and  replacing  them,  so  that  the  original  form  of  the 
wax  may  be  preserved,  otherwise  the  end  thereby  intended  to 
be  secured  will  be  defeated,  and  the  joints  at  these  points  will 
be  irregular  and  unsightly. 

"  For  the  purpose  of  rendering  clear  a  point  necessarily  left 
somewhat  obscure  in  the  foregoing  description,  it  may  be  well 
here  to  state  that  the  space  of  half  a  tooth,  left  between  the 
first  bicuspids  and  the  first  molars,  is  to  compensate  for  shrink- 
age in  the  length  of  the  arch,  for  after  the  first  bicuspids  are 
removed  and  set  adjacent  to  the  first  molars,  thereby  repre- 
senting the  second  bicuspids,  they  occupy  the  entire  vacancy 
first  left  and  one-half  the  space  formerly  occupied  by  said  first 
bicuspids ;  hence  the  extension  of  the  back  moulds  toward  the 
centre  is  equivalent  to  the  shrinkage  of  the  entire  arch. 

"  As  the  foregoing  is  applicable  where  the  case  of  fourteen 
teeth  is  to  be  divided  into  four  blocks,  as  is  usual  in  soldering, 
I  would  say  that  when  the  intention  is  to  make  pin-holes  for 
riveting,  the  space  of  Jut/fa  tooth  must  be  left  between  tlie  canine 
and  bicuspids,  instead  of  between  the  bicuspids  and  molars. 

"The  moulds  for  the  back  teeth  may  now  be  made  in  the 

same  manner  as  those  of  the  front  ones.    After  the  moulds  have 

been  made  as  already  described,  they  should  be  so  trimmed 

that  in  the  process  of  moulding  the  blocks  there  would  be  no 

liability  of  removing  portions  of  the  enamel  oif  the  teeth  in 

withdrawing  the  moulds.    The  moulds  should  now  be  varnished 

with  some  spirit  varnish,  and  after  it  becomes  dry  are  ready 

for  use. 

20 


306  MECHANICAL,   DENTISTEY. 

"  The  moulds  being  prepared,  the  next  step  is  the  enamelling 
of  the  teeth  in  the  moulds.  The  enamels  should  be  moistened 
with  a  little  clean  water,  and  having  previously  oiled  the  sec- 
tion or  sections  of  the  mould,  the  blue  or  point  enamel  may  be 
first  applied  (as  stiff  as  it  will  work)  with  a  very  small  spatula 
made  for  the  purpose.  This  enamel  should  be  thin  at  the  base, 
and  gradually  thickening  with  the  concavity  of  the  mould  to 
the  cutting  edges  of  the  teeth.  The  yellow  or  base  enamel  is 
next  applied  heavy  at  the  base,  and  gradually  terminating  near 
the  point. 

"  After  the  enamelling  has  been  completed  so  far  as  is  de- 
signed to  be  moulded  at  one  time,  a  small  quantity  of  the  body 
about  the  consistency  of  a  thick  paste  may  be  spread  over  the 
surface  of  the  moulds  and  of  the  enamels,  the  moulds  replaced 
upon  the  model,  and  the  body  carefully  filled  in,  at  first  rather 
soft,  but  subsequently  harder  and  harder,  until  the  mould  is 
sufficiently  full.  Then  applying  the  flame  of  a  spirit-lamp 
for  a  few  minutes  with  the  blowpipe,  the  body  will  be  tough- 
ened enough  to  work  well,  when  the  moulds  may  be  removed. 
The  teeth  may  then  be  separated  and  trimmed,  the  blocks  di- 
vided as  desired,  the  gum  enamel  applied,  etc.,  and  so  com- 
pleted. \ 

"  The  process  of  enamelling  and  moulding  being  precisely  the 
same  with  all  the  blocks,  it  needs  not  that  I  should  go  into 
further  detail. 

"  I  have  already  said,  that  when  the  blocks  are  intended  to 
be  riveted  upon  the  plate,  the  moulds  are  required  to  be  some- 
what different.  There  is  also  another  difference ;  that  is,  the 
moulding  of  the  pin  or  rivet  holes,  which  may  be  done  by  re- 
moving the  plate  from  the  model,  placing  the  moulds  upon 
the  model,  and  drilling  a  small  hole  upon  the  prominence  of 
the  ridge  opposite  the  centre  of  each  tooth,  in  which  insert  a 
piece  of  wire  of  a  desired  size.  The  enamelling,  etc.,  may 
then  be  done  as  before  described,  and  after  the  body  has  been 
hardened  sufficiently,  the  pins  may  be  removed,  leaving  the 
holes  neatly  moulded,  perfectly  smooth,  and  straight.  The 
blocks  may  then  be  finished  at  once,  before  removing  from 
the  cast." 


DENTURES   WITH   CONTINUOUS   GUMS.  307 


CHAPTER  XIII. 

Uniting  Single  Porcelain  Teeth  to  Each  Other  and 
TO  A  INIetallic  Base  with  a  Fusible  Silicious  Com- 
pound, FORMING  A  Continuous  Artificial  Gum.* 

The  process  of  uniting  single  mineral  teeth  to  each  other 
and  to  a  metallic  base  by  means  of  a  porcelain  cement,  was 
attempted  as  early  as  1820,  by  Delabarre,  of  Paris,  France, 
but  with  such  imperfect  and  unsatisfactory  results  as  induced 
its  early  abandonment.  At  a  later  period.  Dr.  John  Allen,  a 
distinguished  practitioner  of  dentistry  in  America,  devised  a 
method  embracing  original  and  important  modifications  of 
])ractice  both  in  the  preparation  and  combination  of  materials, 
and  the  modes  of  manipulating  them;  and  after  an  extended 
series  of  experiments,  commencing  in  1844,  succeeded  in  ob- 
taining certain  mineral  compounds  which  vitrified  at  a  heat 
much  below  that  employed  by  Delabarre,  and  the  contraction 
of  which  corresponded  so  nearly  with  that  of  the  platina  base 


*  The  attentive  reader  of  the  first  edition  of  this  work  will  not  fail  to 
note  that  the  statements  involving  the  question  of  priority,  contained  in  the 
introductory  portion  of  the  above  chapter,  are  at  variance  with  those  originally 
published.  A  more  extended  examination  and  careful  analysis  of  tlie  evi- 
dences as  they  appear  upon  record — evidences  not  fully  accessible  to  the 
author  at  the  time  of  the  publication  of  the  first  edition — establish  beyond 
reasonable  doubt  the  just  claims  of  Dr.  Allen  as  the  originator  of  that  special 
and  distinctive  method  here  considered,  by  which  the  attachment  of  the 
teeth  t(>  the  plate  is  effected  liy  direct  fusion  of  the  gum  material.  Dr.  Hun- 
ter's earliest  and  contemporaneous  experiments  contemjilated  simply  a  union 
of  all  the  teeth,  by  means  of  a  fusible  cement,  forming  a  single,  continuous 
block,  which  was  afterwards  united  to  the  l)ase  by  riveting  or  soldering. 

This  brief  explanation  is  here  introduced  as  an  act  of  simple  justice  to 
Dr.  Allen,  who  has  devoted  the  best  energies  of  his  life  to  the  successful  de- 
velopment of  a  process  which  stand*  unrivalled  in  all  tlie  chief  rcciuisites 
of  an  artificial  denture. 


308  MECHANICAL   DENTISTRY. 

to  which  it  was  applied,  that  the  shrinkage  incident  to  baking 
conflicted  in  no  material  degree  with  the  practical  utility  of 
the  work  in  the  mouth. 

In  the  construction  of  dentures  upon  this  principle,  plain 
single  teeth,  made  for  the  purpose,  are  arranged,  and  soldered 
to  a  plate  properly  fitted  to  the  mouth,  after  which  different 
mineral  compounds,  made  to  represent  the  natural  gums,  roof, 
etc.,  are  applied  to  the  plate  and  teeth  in  a  plastic  state,  then 
carved  and  trimmed  in  proper  form,  and  by  means  of  a  strong 
furnace  heat  these  compounds,  which  are  called  the  body  and 
the  gum  enamel,  are  fused,  thus  producing  a  continuous  gum, 
roof,  and  ruga  of  the  mouth,  without  seam  or  crevice. 

The  compounds  at  present  employed  in  this  process,  as  well 
as  the  more  fusible  preparations  used  for  repairing  purposes, 
are  manufactured  in  quantities  sufficient  to  meet  the  wants  of 
the  profession,  and  may  be  procured  at  all  the  dental  furnish- 
ing; houses  throughout  the  United  States. 

The  intimate  but  later  identification  of  Dr.  W.  M.  Hunter 
with  the  above  process  has  rendered  his  name  familiar  as  one 
whose  skill  and  devotion  to  this  specialty  of  mechanical  prac- 
tice has  contributed  to  its  development  in  a  modified  form. 
Dr.  Hunter's  formulas,  and  modes  of  manipulating  his  com- 
pounds, will  be  introduced  hereafter. 

Following  Dr.  Hunter's  descriptions,  the  reader  will  find 
practical  and  valuable  instructions  in  this  method  of  substitu- 
tion, contributed  for  this  edition,  at  the  solicitation  of  the 
author,  by  Dr.  S.  P.  Haskell,  of  Chicago,  Ills.,  and  Professor 
George  S.  Field,  of  Detroit,  Mich.,  both  of  whom  are  recog- 
nized experts,  and  whose  long  experience  and  intimate  famil- 
iarity with  the  most  approved  methods  of  constructing  continu- 
ous gum  dentures  impart  special  value  to  the  subject-matter  of 
their  communications. 

Before  introducing  an  account  of  Dr.  Allen's  modes  of  pro- 
cedure, the  author  would  premise  that  it  is  unnecessary  to 
repeat  in  this  connection  what  has  already  been  fully  described 
in  regard  to  impressions  of  the  mouth,  or  the  manipulations 
connected  witli  the  formation  of  plaster  models  and  metallic 


DE]>,TURES   WITH    CO^'TINUOUS   GUMS.  309 

swages,  these  processes  being  essentially  the  same  as  in  the 
construction  of  ordinary  gold  work.  Whenever  a  rira  is  to  be 
formed  to  the  border  of  the  plate  extending  from  heel  to  heel 
of  the  latter,  and  this  is  to  be  accomplished  by  swaging,  the 
model  should  be  shaped  as  described  in  connection  with  Fig.  37. 
If  it  is  designed  to  enamel  the  entire  lingual  surface  of  the 
plate  (a  method  now  commonly  practiced),  the  shoulder  upon 
the  model  should  be  extended  across  tlie  heel  of  the  latter  from 
each  extremity  of  the  ridge  on  a  line  with  the  posterior  border 
of  the  hard  palate,  to  form  a  groove  in  swaging  similar  to,  and 
continuous  with,  that  on  the  outside  of  the  ridge.  The  edges 
thus  turned  in  swaging  will  flare  more  than  is  required, — the 
operation  must,  therefore,  be  completed  by  carefully  turning 
them  over  sufficiently  with  the  pliers.  In  place  of  swaging 
the  rim,  however,  it  may  be  formed  by  fitting  and  soldering 
along  the  border  a  narrow  plain  strip  of  platinum,  extending 
it  as  before,  if  desired,  across  the  posterior  edge  of  the  plate. 
Or  a  triangular  piece  of  wire  may  be  soldered  on,  bevelled 
somewhat  so  as  to  overhang  the  base  slightly,  thus  forming  a 
shallow  groov^e.  The  border  to  the  palatal  portion  of  the  gum 
at  the  heel  of  the  plate  is  sometimes  formed  in  swaging  by  ad- 
justing a  wire  across  the  heel  of  the  model,  which  will  be 
transferred  to  the  plate  in  the  form  of  a  ridge.  The  latter 
should  be  raised  a  line  or  more  from  the  posterior  border  of 
the  plate,  and  should  incline  gradually  to  the  edge,  while  the 
anterior  surface  should  present  an  abrupt  shoulder  to  the  mar- 
gins of  the  gum  enamel. 

The  process  of  forming  the  rim  is  sometimes  deferred  until 
after  the  first  portion  of  the  body  is  baked,  and  before  the  gum 
enamel  is  applied.  In  this  case,  the  borders  of  the  plate,  to 
the  depth  of  from  a  line  to  a  line  and  a  half,  are  left  uncovered 
by  the  base ;  after  the  latter  has  been  baked,  the  uncovered 
margins  are  turned  over  uj)on  the  ])ody  with  pliers  and  })ur- 
nisher,  and  the  gum  enamel  afterwards  applied  flush  witli  the 
edge  or  surface  of  the  rim. 

In  wJiat(!ver  way  the  rim  or  socket  is  formed,  it  is  j)racti- 
cally  of  the  first  importance  that  the  exact  dimensions  of  the 


310  MECHANICAL    DENTISTRY. 

plate  required  should  be  ascertained  before  the  groove  is 
formed,  as  it  will  be  impossible  to  subsequently  diminish  the 
extent  of  the  borders  without,  to  some  extent,  impairing  the 
integrit}'  of  the  finished  work.  The  mouth,  therefore,  should 
be  carefnlly  examined,  and  the  precise  location,  extent,  and 
fulness  of  the  muscles  and  integuments  along  the  external 
borders  of  the  ridge  above  and  below,  the  glands  underneath 
the  tongue,  and  the  extreme  boundaries  of  the  hard  palate 
carefully  noted  and  accurately  traced  upon  the  plaster  model, 
to  serve  as  a  guide  in  determining  the  dimensions  of  the  plate. 

Additional  strength  will  be  imparted  to  the  metallic  base  by 
doubling  the  central  portion  of  the  plate  as  described  in  Chap- 
ter XI.  The  following  additional  remarks  on  the  method  by 
Dr.  Hunter  are  introduced  : 

"  Platina  as  usually  applied  I  think  objectionable,  wanting 
stiffness;  my  method  of  using  it  is  similar  to  that  proposed  by 
Delabarre,  but  possessing  greater  strength  than  even  his  method, 
and  by  it  can  be  made  as  light  as  a  good  gold  plate  got  up  in 
the  ordinary  way.  I  first  strike  a  very  thin  plate  to  the  cast, 
and  cut  out  a  piece  the  size  of  the  desired  chamber,  taking  care 
not  to  extend  it  forward  to  embrace  the  palatal  artery.  Add 
wax  to  the  plate  for  the  depth  of  the  cavity,  diminishing  it  neatly 
as  it  approaches  the  alveolar  ridge.  Cement  this  plate  to  the 
cast  and  take  another  metallic  cast,  strike  another  thin  plate 
over  the  whole,  and  solder  throughout  with  an  alloy — of  gold 
twenty-two  parts,  platina  two  parts — or  with  pure  gold.  The 
chamber  thus  formed  is  precisely  the  same  as  'Cleveland's 
Patent  Plate,'  but  the  space  between  the  plates,  for  which  he 
obtained  his  patent,  is  subsequently  filled  up,  leaving  a  cavity 
resembling  Gilbert's,  but  with  a  sharper  edge  when  so  desired. 
This  space  is  filled  up  with  base  and  enamel,  and  gives  great 
stiffness  without  the  ugly  protrusion  of  the  struck  chamber. 
The  plate  thus  formed  assimilates  much  more  closely  to  the 
palatal  dome,  not  interfering  with  pronunciation ;  another 
great  advantage  gained  by  it  is  the  impossibility  of  warping. 
I  say  impossibility,  because  I  have  submitted  plates  so  con- 
structed to  the  severest  tests,  and  never  had  them  to  warp. 


DENTURES    AVITH    CONTINUOUS    GUMS.  311 

It  is  well  to  rivet  the  two  plates  together  before  proceeding  to 
solder,  especially  gold  plates,  and  to  bring  the  heat  carefully 
upon  them ;  once  prepared  there  is  no  danger  of  change  in  the 
succeeding  manipulations." 

Dr.  Allen's  Methods. 

The  following  descriptions,  contributed  by  Dr.  Allen,  embrace 
a  clear  and  concise  account  of  the  manipulations  at  present 
practiced  by  him  in  the  construction  of  artificial  dentures  with 
continuous  gums. 

"The  plate  or  base  is  formed  of  platinum,  or  platinum  and 
iridium.  The  plate  being  properly  fitted  to  the  mouth,  and 
wax  placed  upon  it  for  the  bite,  as  in  ordinary  plate  work,  the 
teeth  are  arranged  thereon,  with  special  reference  to  the  require- 
ments of  the  case.  Tliey  are  then  covered  with  a  thin  coating 
of  plaster  mixed  with  water  to  the  consistence  of  cream.  After 
this  has  become  firmly  set,  another  mixture  of  plaster  and 
asbestos  with  water,  somewhat  thicker  or  more  plastic  than  the 
first,  is  placed  round  on  the  outside  of  the  previous  covering 
and  the  plate.  A  convenient  way  of  aj)iilying  the  second  cover- 
ing is  to  turn  the  mixture  out  of  the  vessel  upon  a  piece  of  tin, 
say  four  or  five  inches  square,  thus  forming  a  cone,  upon  which 
tlie  plate,  with  the  teeth  upward,  is  pressed  gently  down  until 
within  an  inch  or  less  from  the  tin.  Then  with  a  spatula  the 
mixture  is  brought  up  over  the  teeth,  forming  an  investient  that 
will  not  crack  in  the  process  of  soldering.  Sand  may  be  used 
with  the  plaster  for  this  purpose,  but  I  think  asbestos  preferable. 

"  When  the  covering  has  become  sufficiently  hard,  the  wax 
is  removed,  and  a  rim  of  platinum  is  then  fitted  to  the  lingual 
side  of  the  teeth,  below  the  pins,  and  to  the  base  plate.  The 
pins  in  the  teeth  are  then  bent  down  upon  the  rim,  and  sold- 
ered with  pure  gold,  or  a  mixture  of  gold  and  platinum,  at 
the  same  time  the  rim  is  soldered  to  the  plate.  This  rim,  which 
forms  tfie  lining  for  the  teeth,  is  usually  about  the  thickness  of 
tlie  plate  upon  which  they  are  set,  say  twenty-eight  to  thirty ; 
but  should  the  case  require  more  than  ordinary  strength,  a 
double  or  triple  thickness  of  rim  should  be  used.     This  may 


312  MECHANICAL    DENTISTEY. 

become  necessary  in  cases  where  the  natural  rnolar  teeth  are 
standing  firmly  in  the  opposite  jaw,  and  antagonize  with  the 
artificial  piece,  or  where  from  any  cause  an  undue  strain  is 
brought  to  bear  upon  the  artificial  teeth.  To  attain  successful 
results,  the  dentist  must  take  into  consideration  all  the  circum- 
stances or  conditions  of  each  particular  case,  and  then  exercise 
his  best  judgment  in  executing  the  work. 

"  In  soldering  platinum  with  pure  gold,  flat  surfaces  of  this 
metal  should  be  brought  in  positive  contact,  in  order  to  become 
firmly  united.  Therefore  in  mounting  teeth  upon  a  plate  of 
this  kind  the  backing  or  inside  rim  should  be  a  little  wider  than 
the  distance  between  the  pins  in  the  teeth  and  the  plate,  say 
from  an  eighth  to  a  fourth  of  an  inch.  This  extra  width  of  rim 
should  be  bent  at  right  angles  along  the  base  of  the  teeth,  so  as 
to  admit  of  being  pressed  down  upon  the  plate  after  the  rim  is 
adjusted  to  the  teeth,  and  the  pins  bent  down  firmly  upon  it. 
In  this  way  flat  surfaces  of  the  rim  and  plate  are  brought  to- 
gether and  soldered.  The  pins  in  the  teeth  are  also  soldered  to 
the  rim  at  the  same  time.  When  the  parts  are  thus  united, 
they  will  remain  so  during  the  subsequent  bakings;  but  if  the 
edge  of  the  rim  only  is  fitted  to  the  plate  and  soldered  like  gold 
or  silver  work,  the  subsequent  heatings  for  baking  the  body  and 
gum  will  cause  the  gold  to  become  absorbed  in  the  platinum, 
and  leave  the  joints  not  united.  It  may  be  asked.  Why  not  use 
common  gold  solder  for  this  style  of  work?  Answer,  Because 
the  alloy  in  the  solder  will  greatly  injure  the  color  of  the  gum 
enamel  in  baking.  Copper  alloy  will  turn  it  to  a  greenish  shade, 
and  silver  Avill  give  it  a  yellow  tinge.  Although  pure  gold 
requires  more  intense  heat  to  melt  it  (being  about  two  thousand 
degrees)  than  ordinary  gold  solder,  yet  when  melted  it  flows  much 
more  freely  than  the  latter.  The  best  way  to  solder  the  teeth 
upon  platinum  plate  is,  to  place  small  pieces  of  gold  upon  the 
joints  or  parts  to  be  soldered,  with  wet  ground  borax,  and  then 
slowly  introduce  the  piece  with  the  investient  into  a  heated 
muffle,  and  bring  the  whole  mass  up  to  a  red  heat ;  then  with- 
draw it  from  the  furnace,  and  bring  it  quickly  under  the  blow- 
pipe to  flow  the  gold.     In  this  way  the  teeth  do  not  become 


DENTURES   WITH    COXTINUOUS   GUMS.  313 

etched,  as  they  are  liable  to  be  if  the  soldering  is  done  in  the 
furnace. 

"  The  piece  being  soldered  and  cooled,  the  covering  is  re- 
moved from  the  teeth,  taking  care  to  preserve  the  base  un- 
broken for  the  plate  to  sit  upon  during  the  subsequent  bakings 
of  the  body  and  gum  enamel. 

"All  particles  of  plaster  or  other  foreign  matter  should  be 
removed  from  the  teeth  and  plate  by  thoroughly  washing  and 
brushing  them.  It  is  well  to  immerse  the  piece  for  a  short 
time  in  sulphuric  acid,  after  which  rinse  and  brush  it  well 
with  water.  This  done,  a  colorless  mineral  compound,  called 
the  body,  is  applied  in  a  plastic  state  (with  spatulas  or  small 
instruments  for  the  purpose)  to  the  teeth  and  plate.  It  is  then 
carved  to  represent  the  gum,  roof,  and  rugae  of  the  mouth, 
taking  care  to  keep  the  crowns  of  the  teeth  well  defined.  The 
piece  is  then  placed  on  the  base  upon  which  it  was  soldered, 
and  set  upon  a  slide  on  the  apron  in  front  of  one  of  the  upper 
muffles  of  the  heated  furnace, — and  every  eight  or  ten  minutes 
it  should  be  moved  forward  into  the  muffle,  say  two  or  four 
inches  each  time,  until  the  piece  shall  have  passed  the  centre 
of  the  same,  which  should  be  at  a  red  heat.  It  is  then  with- 
drawn and  passed  into  a  lower  muffle,  where  the  heat  is  greater, 
in  which  the  body  soon  becomes  semivitrified,  which  is  suffi- 
cient for  the  first  bake.  It  is  then  taken  out  and  (together 
with  the  slide  on  which  it  was  baked)  placed  in  a  cooling  muf- 
fle, the  mouth  of  which  should  be  closed  to  prevent  the  change 
of  t(!mperature  from  being  too  rapid,  and  causing  the  teeth  to 
become  brittle.  When  the  piece  is  sufficiently  cool  to  handle, 
a  second  a))plication  of  body  is  made  for  the  purpose  of  re- 
pairing any  defects  that  may  have  occurred  in  the  baking;  this 
done,  the  piece  is  again  introduced  as  before  into  the  upper 
muffle,  then  in  the  lower,  allowing  the  second  bake  to  be(!omc 
a  little  harder  than  the  first,  but  not  so  much  as  to  appear 
glossy.     It  is  then  withdrawn,  and  cooled  as  described  above. 

"A  flesh-colored  compound  is  then  applied,  which  is  called 
the  gum  enamel.  This  is  also  made  j)lastic  with  water,  and 
a  thin  coating  is  put  over  the  body,  and  closely  packed  and 


314  MECHANICAL   DENTISTRY. 

carved  around  the  teeth  with  small  instruments  made  for  the 
purpose, — still  taking  care  to  keep  the  crowns  of  the  teeth 
clean  and  well  defined.  Small  camel's-hair  brushes  are  used 
wet  with  water,  to  cause  the  gum  enamel,  and  also  the  body, 
to  settle  more  closely  around  the  necks  of  the  teeth ;  other 
brushes  are  also  used  dry  to  remove  all  particles  of  body,  gum, 
or  other  substances  from  the  crowns  of  the  teeth. 

"  After  the  application  of  the  gum  enamel,  the  piece  is  again 
subjected  to  the  heat  of  the  furnace  as  described  for  baking  the 
body,  with  this  difference :  The  heat  should  be  a  little  greater 
than  for  either  of  the  preceding  bakes.  It  should  be  a  strong, 
sharp  heat,  in  order  to  produce  a  smooth  glossy  appearance, 
which  is  required  for  the  enamel.  These  different  degrees  of 
heat  for  the  first,  second,  and  third  bakings  should  be  carefully 
observed  for  the  purpose  of  getting  an  even  temper  in  the  piece, 
and  thereby  preventing  it  from  crazing  or  cracking  in  cooling. 

"  The  enamel  being  thoroughly  fused,  the  piece  is  withdrawn 
from  the  heated  muffle,  and  passed  into  another,  outside  of  the 
furnace.  This  muffle  should  be  made  quite  hot  before  the 
denture  is  placed  in  it,  in  order  to  prolong  the  cooling  process ; 
for  if  the  piece  is  cooled  too  rapidly  it  is  rendered  more  fragile. 
It  is  well  to  let  the  case  remain  in  the  cooling  muffle,  with  the 
mouth  of  it  closed,  several  hours  before  exposing  it  to  the  air. 
By  baking  just  at  night  the  piece  will  be  in  proper  condition 
to  finish  up  the  next  morning. 

"  The  finishing  process  consists  simply  in  smoothing  and 
polishing  the  plate,  and  burnishing  the  rim.  It  is  then  ready 
to  be  adjusted  to  the  mouth.  In  baking,  great  care  is  necessary 
to  prev-ent  the  piece  from  becoming  gassed.  This  can  be  avoided 
by  allowing  the  gas  to  escape  entirely  from  the  burning  coal 
or  coke  i;i  the  furnace  before  the  piece  is  introduced  into  the 
muffle.  The  presence  of  gas  is  indicated  by  the  blue  flame 
escaping  from  the  coal.  When  the  fire  becomes  clear,  it  is 
then  safe  to  introduce  the  case  to  be  baked  (as  before  described) 
into  the  muffle.  Pure  anthracite  coal  is  the  best  for  this  pur- 
pose, as  it  maintains  a  longer  and  stronger  heat  than  coke. 


DENTUEES    WITH    CONTINUOUS    GUMS.  315 

Bituminous  coal  is  not  good  for  this  kind  of  work  unless  first 
converted  into  coke. 

"  It  often  occurs  that  the  natural  gums  will  change  more  or 
less  after  the  teeth  are  inserted.  In  such  cases  a  new  impres- 
sion should  be  taken  from  the  mouth,  and  a  fusible  die  formed. 
The  denture  is  then  placed  upon  the  die,  and  it  will  be  seen  at 
once  where  the  change  has  taken  place;  then  with  the  piece 
resting  upon  the  die  the  artificial  gum  maybe  chipped  off  with 
a  small  hammer  and  chisel.  The  platinum  plate  being  soft 
can  be  refitted  to  the  die  very  accurately  with  a  burnisher, 
hammer,  and  small  driver  made  for  the])urpose.  A  new  coat 
of  body  is  then  applied  where  the  plate  has  been  refitted,  and 
then  baked,  cooled,  enamelled,  and  baked  again, — still  observ- 
mgr  the  same  directions  as  detailed  in  the  management  of  new 
pieces. 

"  If  the  tooth  gets  broken  (a  mishap  which  seldom  occurs  by 
use  in  the  mouth),  it  can  be  replaced  with  another,  by  grind- 
ing out  the  remaining  portion  of  the  broken  tooth,  and  the 
gum  which  covers  the  fang,  and  then  fitting  a  new  one  in  the 
place.  This  tooth  need  not  be  soldered  to  the  inside  rim;  it  is 
sufficient  to  o;rind  a  small  notch  or  g-roove  in  the  enamel  which 
covers  the  lingual  side  of  the  rim  for  the  pin  of  the  tooth  to  fit 
into.  The  pin  resting  in  the  groove  is  covered  with  the  body 
at  the  same  time  it  is  applied  around  the  base  of  the  tooth,  and 
when  this  body  is  baked  the  tooth  will  become  firmly  fastened 
in  place  of  the  broken  one.  Any  number  of  teeth  that  may 
be  required  can  be  replaced  in  this  way.  If  it  is  desired  to 
change  the  position  of  one  or  more  teeth,  or  to  make  them  longer, 
this  can  also  be  done  as  described  above,  with  this  additional 
precaution,  which  is  simply  to  press  softened  wax  upon  the 
inside  of  the  teeth  and  palatal  arch  of  the  denture  before  the 
others  are  removed, — this  wax  will  serve  as  a  guide  or  index 
as  to  the  relative  change  to  be  made,  and  also  to  sustain  the 
teeth  in  place  while  they  are  being  fitted  as  desired  to  the  den- 
ture. The  wax  soon  becomes  hard,  and  is  readily  removed  as 
each  sucrcssive  tooth  is  ground  and  adjusted  in  its  proper  place. 

"  When  the  teeth  are  thus  fitted  with  each  pin  accurately 


316  MECHANICAL   DENTISTRY. 

pressed  into  the  groove  prepared  for  it,  and  the  wax  being 
placed  upon  the  inside  to  support  the  teeth  in  proper  posi- 
tion,— body  is  filled  in  around  the  base  of  the  new  ones,  which 
are  carved,  trimmed,  and  brushed,  so  as  to  save  the  crowns  of 
the  teeth  clean  and  properly  defined.  The  wax  is  then  care- 
fully removed  from  the  piece,  and  more  body  is  filled  in  around 
the  teeth  upon  the  inside,^ — ^filling  up  the  grooves  over  the  pins, 
and  then  carving,  trimming,  etc.,  as  before,  to  give  it  the  de- 
sired form.  This  done,  if  the  teeth  are  set  a  little  apart,  and 
it  is  desired  to  keep  them  in  that  position,  take  a  small  piece 
of  asbestos  and  gently  press  it  in  between  the  teeth  at  the  cut- 
ting edges ;  this  will  prevent  them  from  being  drawn  together 
when  the  body  is  being  baked.  The  piece  is  now  ready  for 
the  furnace,  but  it  should  not  be  baked  hard  enough  to  gloss 
the  newly  applied  body ;  it  should  have  more  the  appearance 
of  Parian  marble. 

"  This  beino;  done,  it  is  then  withdrawn  from  the  furnace 
and  transferred  to  a  cooling  muffle  as  before  described.  When 
sufficiently  cool,  the  gum  enamel  is  applied  and  baked  with  a 
sharp  heat  until  it  becomes  smooth  and  glossy.  To  prevent 
the  old  gum  from  bleaching  or  becoming  lighter  colored  in 
consequence  of  repeated  bakings,  a  very  thin  coating  of  fresh 
gum  enamel  should  be  lightly  brushed  over  the  entire  en- 
amelled surface  of  the  piece.  The  enamel  thus  applied  should 
be  mixed  with  water,  quite  thin,  so  as  to  flow  evenly  over  the 
surface  when  applied  with  a  camel's-hair  brush.  This  should 
be  done  before  the  last  baking,  that  the  whole  may  be  fused  at 
the  same  time.  Experience  and  judgment  are  essential  requi- 
sites in  order  to  produce  good  practical  results.  For  example, 
if  the  carving  of  the  body  is  not  properly  done,  the  form  and 
shading  of  the  gum  and  roof  will  not  appear  natural  when  the 
work  is  finished  ;  if  the  gum  enamel  is  put  on  too  thick  it  will 
produce  a  dark-red  color ;  if  not  thick  enough  it  will  be  too 
light ;  if  fused  too  hard  it  will  be  liable  to  craze  or  crack ;  if 
not  hard  enough  it  will  be  rough  or  granular;  if  the  piece  be- 
comes gassed  in  baking  it  will  be  porous  and  of  a  bluish  color. 
Again,  the  teeth  of  different  persons  vary  as  much  as  any  fea- 


DENTURES   WITH   CONTINUOUS   GUMS.  817 

ture  of  the  face,  and  present  as  great  a  variety  of  expressions. 
Therefore,  in  the  construction  of  artificial  dentures,  the  dentist 
should  select  and  arrange  the  teeth  with  special  reference  to 
each  individual  case.  The  length,  size,  form,  shade,  and  posi- 
tion of  the  teeth  should  be  varied  to  meet  all  the  different 
physiognomical  requirements  tliat  occur  in  dental  practice. 

"  This  system  also  combines  with  great  advantage  the  restora- 
tion of  the  face  in  cases  where  the  muscles  have  become  sunken 
or  fallen  in  from  the  loss  of  the  teeth  and  consequent  absorp- 
tion of  the  alveolar  processes.  Here,  again,  the  artistic  skill 
of  the  dentist  is  brought  into  requisition.  He  should  study  the 
face  of  his  patient  as  the  artist  studies  his  picture,  for  he  dis- 
jjlays  his  genius  not  upon  canvas  but  ui)on  the  living  features 
of  the  face ;  and  of  how  much  more  importance  is  the  living 
picture,  that  reflects  even  the  emotions  of  the  heart,  than  the 
lifeless  form  upon  canvas.  He  should  know  the  origin  and 
insertion  of  every  muscle  of  which  the  face  is  formed,  and  what 
ones  he  is  to  raise,  otherwise  he  will  be  liable  to  produce  dis- 
tortion instead  of  restoration.  This  improvement  consists  of 
prominences  made  upon  the  denture  of  such  form  and  size  as 
to  bring  out  each  muscle  or  sunken  portion  of  the  face  to  its 
original  fulness ;  and  when  these  are  rightly  formed  they  are 
not  detected  by  the  closest  observer.  There  are  four  points  of 
the  face  (of  many  persons)  which  the  mei-e  insertion  of  the  teeth 
does  not  restore,  viz.,  one  upon  each  side  beneath  the  malar  or 
cheek-bone,  and  also  a  jwiut  upon  each  side  of  the  base  of  .the 
nose,  in  a  line  toward  the  front  portion  of  the  malar  bone. 

"The  extent  of  this  falling-in  varies  in  different  persons, 
according  to  their  temperaments.  If  the  ]ym[)hatic  tempera- 
ment predominates,  the  diange  will  be  slight.  If  nervous  or 
sanguine,  it  may  be  very  great.  .The  muscles  situated  upon  the 
sides  of  the  face,  and  which  rest  upon  the  molar  or  back  teeth, 
are  tlie  zygomaticus  major,  masseter,  and  buccinator.  The  loss 
of  the  above  teeth  cause  these  muscles  to  fall  in.  The  princi- 
pal muscles  which  form  the  front  portion  of  the  face  and  lips 
are  the  zygomaticus  minor,  hivator  labii  superioris  alaeque  nasi, 
and  orbicularis  oris. 


318  MECHANICAL   DENTISTEY. 

"  These  rest  upon  the  front,  eye,  and  bicuspid  teeth,  which, 
when  lost,  allow  the  muscles  to  sink  in,  thereby  changing  the 
form  and  expression  of  the  mouth. 

"The  insertion  of  the  front  teeth  will  in  a  great  measure 
bring  out  the  lips,  but  there  are  two  muscles  in  the  front  por- 
tion of  the  face  which  cannot,  in  many  cases,  be  thus  restored 
to  their  original  position  ;  one  is  the  zygomaticus  minor,  which 
arises  from  the  front  part  of  the  malar  bone,  and  is  inserted  into 
the  uj^jper  lip  above  the  angle  of  the  mouth ;  the  other  is  the 
levator  muscle,  which  arises  from  the  nasal  process  and  from 
the  edge  of  the  orbit  above  the  infraorbitar  foramen.  It  is 
inserted  into  the  ala  nasi  or  wing  of  the  nose  and  upper  lip. 

"  The  prominences  before  mentioned,  applied  to  these  four 
points  of  the  face,  beneath  the  muscles  just  described,  bring  out 
that  narrowness  and  sunken  expression  about  the  upper  lip  and 
cheeks  to  the  same  breadth  and  fulness  which  they  formerly 
displayed.  If  skill  and  judgment  have  presided  over  all  parts 
of  the  operation,  the  result  will  be  highly  pleasing,  and  of 
practical  utility."* 

Dr,  Hunter^  Formulas  and  3Iodes  of  Practice. — The  fol- 
lowing methods  of  compounding  and  applying  the  continuous 
gum  materials,  as  practiced  by  Dr.  W.  M.  Hunter,  are  repro- 
duced from  his  latest  published  descriptions  in  1852. 

The  following  is  a  description  of  the  materials  and  com- 
pounds employed : 

"  Silex  should  be  of  the  finest  and  clearest  description,  and 
kept  on  hand  ready  ground,  the  finer  the  better. 

^'  Fused  spar  should  be  the  clearest  felspar,  such  as  is  used 

*  Inasmuch  as  the  improvement  for  restoring  the  face  has  been  claimed 
by  others,  the  reader  is  referred  for  the  evidences  establishing  the  claim  of 
Dr.  Allen  to  priority  of  invention  to  the  historical  record  which  appears  in 
the  old  American  Journal  of  Dental  Science  of  1845.  In  the  published  pro- 
ceedings of  the  American  Society  of  Dental  Surgeons  of  that  year,  it  will  be 
seen  that  a  medal  was  awarded  to  one  of  its  members,  inscribed,  "  Awarded 
to  Dr.  John  Allen,  for  his  invention  for  restoring  the  contour  of  the  face, 
August,  1845."  This,  in  connection  with  the  fact  that  no  other  record  upon 
this  subject  is  found  in  our  dental  literature,  fixes  the  date  of  this  improve- 
ment. 


DENTURES   WITH   CONTINUOUS  GUMS.  319 

by  tooth  manufacturers  for  enamels,  completely  fused  in  a 
porcelain  furnace,  and  ground  fine. 

"  Calcined  borax'is  prepared  by  driving  off  the  water  of  crys- 
tallization from  the  borax  of  commerce,  by  heating  in  a  covered 
iron  vessel  over  a  slow  tire,  and  it  is  better  to  use  immediately 
after  its  preparation,  as  it  attracts  moisture.  It  should  be 
perfectly  clean  and  white,  and  free  from  lumps. 

"  Caustic  Potas.'ta  Optimus. — Known  also  as  potassa  fusa. 

"  Asbestos. — Take  the  ordinary  clean  asbestos,  free  it  from 
all  fragments  of  talc  or  other  foreign  substances,  and  grind  fine, 
taking  care  to  remove  any  hard  fragments  that  may  occur. 

"  Granulated  Body. — Take  any  hard  tooth  material  (I  use 
the  following  formula:  spar  3  ozs.,  silex  1|  ozs.,  kaolin  ^  oz.) 
and  fuse  completely.  Any  very  hard  porcelain,  wedge  wood 
ware,  or  fine  ciiina  will  answer  the  same  purpose.  Break  and 
grind  so  that  it  will  pass  through  a  wire  sieve,  No.  50,  and 
again  sift  off  the  fine  particles  which  will  pass  through  No.  10 
bolting  cloth.  It  is  then  in  grains  about  as  fine  as  the  finest 
gunpowder. 

^'  Flux. — Upon  this  depends  the  whole  of  the  future  opera- 
tions, and  too  much  care  cannot  be  taken  in  its  preparation. 
It  is  composed  of  silex  8  oz.,  calcined  borax  4  oz,,  caustic  po- 
tassa 1  oz.  Grind  the  potassa  fine  in  a  wedgewood  mortar ; 
gradually  add  the  other  materials  until  they  are  thoroughly 
incorporated.  Line  a  Hessian  crucible  (as  white  as  can  be  got) 
with  pure  kaolin,  fill  with  the  mass,  and  lute  on  as  a  cover 
a  piece  of  fire-clay  slab  with  the  same.  Expose  to  a  clear 
strong  fire  in  a  furnace  with  coke  fuel  for  about  half  an  hour, 
or  until  it  is  fused  into  a  transparent  glass,  which  should  be 
clear  and  free  from  stain  of  any  kind,  more  especially  when 
it  is  used  for  gum  enamels.  Break  this  down,  and  grind  until 
fine  enough  to  pass  through  a  bolting  cloth,  when  it  will  be 
ready  for  use. 

"  JJase. — Take  flux  1  oz.,  asbestos  2  oz.,  grind  together  very 
fine,  completely  intermixing.  Add  granulated  body  1^  oz., 
and  mix  with  a  spatula  to  prevent  grinding  the  granules  of 
IxxJy  any  finer. 


320  MECHANICAL   DENTISTEY. 

"  Gum  Enamels. — No.  1.  Flux  1  oz.,  fused  spar  1  oz.,  English 
rose  40  grains.  Grind  the  English  rose  extremely  fine  in  a 
wedgewood  mortar,  and  gradually  add  the  flux  and  then  the 
fused  spar,  grinding  until  the  ingredients  are  thoroughly  in- 
corporated. Cut  down  a  large  Hessian  crucible  so  that  it  will 
slide  into  the  muffle  of  a  furnace,  line  with  silex  and  kaolin 
each  one  part,  put  in  the  material,  and  draw  up  the  heat  on 
it  in  a  muffle  to  the  point  of  vitr  if  action,  not  fusion,  and  with- 
draw from  the  muffle.  The  result  will  be  a  red  cake  of  enamel, 
which  will  easily  leave  the  crucible,  which,  after  removing  any 
adhering  kaolin,  is  to  be  broken  down  and  ground  tolerably 
fine.  It  may  now  be  tested,  and  then  (if  of  too  strong  a  color) 
tempered  by  the  addition  of  covering.  This  is  the  gum  which 
flows  at  the  lowest  heat,  and  is  never  used  when  it  is  expected 
to  solder. 

"  No.  2.  Flux  1  oz.,  fused  spar  2  oz.,  English  rose  60  grains. 
Treat  the  same  as  No.  1.  This  is  a  gum  intermediate,  and  is 
used  upon  platina  plates. 

"  No.  3.  Flux  1  oz.,  fused  spar  3  oz.,  English  rose  80  grains. 
Treat  as  the  above.  This  gum  is  used  in  making  pieces  in- 
tended to  be  soldered  on,  either  in  full  arches  or  in  the  sections 
known  as  hloch-ioork.  It  is  not  necessary  to  grind  very  fine  in 
preparing  the  above  formulas  for  application. 

"■  Covering. — What  is  termed  covering  is  the  same  as  the 
formulas  for  gum,  minus  the  English  rose,  and  is  made  without 
any  coloring  whatever  when  it  is  used  for  tempering  the  above 
gums  which  are  too  highly  colored,  and  which  may  be  done 
by  adding,  according  to  circumstances,  from  1  part  of  covering 
to  2  of  gum,  to  3  of  covering  to  1  of  gum,  thus  procuring  the 
desired  shade.  When  it  is  to  be  used  for  covering  the  base 
prior  to  applying  the  gum  it  may  be  colored  with  titanium, 
using  from  two  to  five  grains  to  the  ounce. 

"  Investient — Take  two  measures  of  white  quartz  sand,  mix 
with  one  measure  of  plaster  of  Paris,  mixing  with  just  enough 
water  to  make  the  mass  plastic,  and  apply  quickly.  The  slab 
on  which  the  piece  is  set  should  be  saturated  with  water,  to 


DENTURES    WITH    CONTINUOUS   GUMS.  321 

keep  the  material  from  setting  too  soon,  and  that  it  may  unite 
with  it. 

"  Cement. — Wax  1  oz.,  rosin  2  oz.  The  proportions  of  this 
will  vary  according  to  the  weather ;  it  should  be  strong  enough 
to  hold  the  teeth  firmly,  and  yet  brittle  enough  to  chip  away 
freely  when  cold.  A  little  exjjerience  will  enable  any  one  to 
prepare  it  properly." 

(Inasmuch  as  the  method  of  constructing  the  platinum  base, 
with  Cleveland's  modification  of  chamber  as  described  by  Dr. 
H.,  has  already  been  introduced,  this  portion  of  the  descrip- 
tion is  omitted  in  this  connection.) 

"  After  the  plates  are  perfectly  adapted  to  the  mouth,  place 
wax  upon  each,  which  trim  to  the  proper  outline  as  regards 
length  and  contour  of  countenance,  marking  the  proper  occlusion 
of  the  jaws  and  the  median  line.  These  waxen  outlines  are 
CJalled  the  drafts,  and  are  carefully  removed  from  the  mouth, 
and  an  articulator  taken  bv  which  to  arrange  the  teeth. 

"  When  the  absorption  is  considerable  and  the  plate  in  con- 
sequence is  rather  flat,  it  is  necessary  to  solder  a  band  or  rim 
along  the  line  where  the  upper  draft  meets  the  plate,  about 
one-sixteenth  or  one-eighth  of  an  inch  wide,  and  fitting  up 
against  the  outline  of  the  draft.  When  the  ridge  is  still  prom- 
inent, the  block  will  not  of  course  be  brought  out  against  the 
lip  so  much,  and  a  wire  may  be  soldered  on  instead  of  the 
wider  band.  I  think  one  or  the  other  necessary,  as  it  gives  a 
thick  edge  to  the  block,  rendering  it  far  less  liable  to  crack  off 
than  if  it  were  reduced  to  a  sharp  angle;  it  also  allows  the 
edge  of  the  plate  to  be  bent  in  against  the  gum,  or  away  from 
it,  as  circumstances  may  require,  and  affords  in  many  cases  a 
far  iK'ttr-r  support  for  the  plates  than  can  be  given  to  one  in 
which  the  band  is  druck  up,  or  the  edge  turned  over  witli  pliers, 
where  the  block  must  extend  to  the  edge  of  the  plate.  Some 
few  cases  do  occur  when  the  band  may  be  struck  as  far  back 
as  tlic  bicuspids  with  advantage,  and  some  in  the  lower  jaw 
where  it  is  nece-ssary  to  solder  on  the  band,  but  the  general 
practi(;c  is  not  so. 

"The  upper  teeth  are  first  arranged  on  the  plate  uiitago- 

21 


322  MECHANICAL   DENTISTRY. 

nizing  with  the  lower  draft,  supported  by  wax  or  cement,  or 
both.  Then  remove  the  lower  draft  and  arrange  the  lower 
teeth  so  that  the  coaptation  of  the  cutting  edges  of  the  teeth 
shall  be  perfect  as  desired.  The  patient  may  now  be  called  in 
again,  and  any  change  in  the  arrangement  made  to  gratify  his 
or  her  taste  or  whim.  Now  place  the  plates  with  the  teeth 
thereon,  on  their  respective  casts,  oil  the  cast  below  the  plate 
and  apply  plaster  of  Paris  over  the  edge  and  face  of  the  teeth 
and  down  on  the  cast,  say  an  inch  below  the  edge  of  the  plate. 
This  will  hold  them-  firmly  in  their  place  while  you  remove 
the  wax  and  cement  from  the  inside,  and  fit  and  rivet  backs  to 
the  teeth.  When  backed,  cut  the  plaster  through  in  two  or 
more  places,  and  remove.  Clean  the  plate  by  heating.  Cut 
the  plaster  so  that  while  it  will  enable  you  to  give  each  tooth 
its  proper  position,  you  can  readily  remove  it  from  the  teeth 
when  they  are  cemented  to  the  plate.  Adjust  the  sections  of 
plaster  and  the  teeth  in  their  proper  positions.  The  plaster 
may  be  held  by  a  piece  of  soft  wire.  Cement  the  teeth  to  the 
plate  and  strengthen  the  cement  by  laying  slips  of  wood  half 
an  inch  long  along  the  joint  and  against  the  teeth.  (I  gene- 
rally use  the  matches  which  are  so  plenty  about  the  laboratory.) 
Remove  the  sections  of  plaster,  being  careful  not  to  displace 
any  of  the  teeth.  If  it  be  intended  to  cover  the  strap  with 
enamel,  you  should  solder  a  wire  after  backing,  and  previous 
to  replacing  the  teeth,  along  the  plate  parallel  with  the  bottom 
of  the  straps,  and  about  ^  or  J  of  an  inch  from  them. 

"  The  teeth  are  now  backed  and  cemented  to  the  plate,  and 
present  an  open  space  between  the  plate  and  the  teeth,  which  is 
to  be  filled  up  with  the  base,  using  it  quite  wet  to  fill  up  the 
small  interstices,  filling  in  the  rest  as  hard  and  dry  as  possible. 
Fill  the  cavity  between  the  plates  in  the  same  manner,  and  oil 
the  edge.  Oil  the  surface  of  the  base,  envelop  in  the  investient 
(precisely  as  you  Avould  put  an  ordinary  job  into  plaster  and 
sand  for  soldering),  and  set  on  a  fire-clay  slab  pr-eviously  satu- 
rated with  water.  When  hard  chip  away  the  cement,  cooling 
it  if  necessary  with  ice,  until  it  is  perfectly  clean.  Along  the 
joints  place  scraps  and  filings  of  platina  very  freely,  and  cover 


DENTURES    WITH    CONTINUOUS   GUMS.  323 

all  the  surface  you  wish  to  enamel  with  coarse  filings,  holding 
them  to  their  place  by  borax  ground  fine  with  water.  Apply 
pure  gold  as  a  solder  quite  freely,  say  two  dwt.  or  more  to  a 
single  set.  Put  in  a  muffle  and  bring  up  a  gradual  heat  until 
the  gold  Rows  freely,  which  heat  is  all  that  will  be  needed  for 
the  base ;  withdraw  and  cool  in  a  muffle.  Remove  the  invest- 
ient  and  fill  up  all  crevices  and  interstices  not  already  filled, 
with  covering  No.  2  ;  cover  the  straps  and  base  with  the  same, 
about  as  thick  as  a  dime,  and  cover  this  with  gum  No.  2  about 
half  that  thickness.  At  the  same  time  enamel  the  base  in  the 
chamber,  and  cover  with  thick  soft  paper.  Set  the  plate  down 
on  the  investient  on  a  slab,  with  the  edges  of  the  teeth  up. 
Fuse  in  a  muffle,  and  the  work  is  completed.  Blemishes  may 
occur  in  the  gum  from  a  want  of  skill  in  the  manipulation; 
should  such  occur,  remedy  by  applying  gum  No.  1. 

"  Should  the  patient  object  to  the  use  of  platina  as  a  base,  the 
work  can  be  made  as  above  on  an  alloy  of  gold  and  platina 
20  carats  fine,  and  soldered  with  pure  gold,  etc.,  as  above.  In 
all  cases,  however,  where  it  is  used,  the  upper  plate  should  be 
made  as  I  have  described  above,  but  with  platina  any  kind  of 
plate  can  be  used. 

"Ordinary  Alloy. — Blocks  may  be  made  and  soldered  to  the 
ordinary  plate  if  the  absorption  is  sufficient  to  require  much 
gum,  without  any  platina.  Arrange  the  teeth  on  wax  on  the 
plate,  fill  out  the  desired  outline  of  gum,  and  apply  plaster  one- 
fourth  of  an  inch  thick  over  the  face  of  the  teeth,  wax  and  cast. 
When  hard,  cut  it  into  sections  (cutting  between  the  canines 
and  bicuspids),  remove  the  wax  from  the  plate  and  teeth,  bind 
the  .sections  of  the  plaster  mould  thus  made  to  their  places  with 
a  wire,  oil  its  surface  and  that  of  the  plate,  fill  in  the  space 
beneath  the  teeth  with  the  base,  wet  at  first,  but  towards  the  last 
as  hard  and  dry  as  possible,  and  thoroughly  compacted.  Trim 
to  the  desired  outline  on  the  inside,  oil  the  base,  and  fill  the  whole 
palatal  spa(;e  with  investient,  supporting  the  block  on  its  lingual 
side.  Remove  the  plaster  mould,  and  cut  through  the  block 
with  a  very  thin  blade  between  the  canines  and  bicuspids. 
Take  the  whole  job  off  of  the  plate,  and  set  on  a  fire-clay  slab 


324  MECHANICAL   DENTISTRY. 

with  investient,  the  edges  of  the  teeth  clown ;  bring  up  the  heat 
in  a  muffle  to  the  melting-point  of  pure  gold.  When  cold, 
cover  and  gum  with  No.  3  gum  and  covering. 

"  Another  mode  is  to  back  the  sections  with  a  continuous 
strap  (using  only  the  lower  pin),  fill  in  the  base  from  the  front, 
use  covering  and  gum  No.  3,  finish  at  one  heat.  When  the 
blocks  are  placed  upon  the  plate,  the  other  pin  is  used  to  fasten 
the  gold  back,  which  is  soldered  to  it  and  the  platina  half-back ; 
neither  of  these  backs  need  be  very  heavy,  as  soldering  the  two 
together  gives  great  strength  and  stiffness.  Very  delicate  block- 
work  can  be  made  in  this  way,  and  it  is  applicable  also,  where 
a  few  teeth  only  are  needed. 

"  A  very  pretty  method,  where  a  section  of  two  or  four  teeth 
(incisors)  is  needed,  and  only  a  thin  flange  of  gum,  is  to  fit  gum 
teeth  into  the  space,  unite  by  the  lower  platina  with  the  con- 
tinuous back,  and  unite  the  joint  with  gum  No.  3.  A  tooth  left 
ungummed  by  the  manufacturer  would  be  best  for  the  pur- 
pose. The  same  may  be  applied  to  blocks  for  a  full  arch, 
remembering  not  to  depend  entirely  upon  platina  backs. 

"  The  method  I  prefer  for  full  arches  on  ordinary  plate,  is 
to  take  a  ribbon  of  platina,  a  little  Avider  than  the  intended 
base,  and  of  the  length  of  the  arch,  cut  it  nearly  through  in 
five  places,  viz.,  between  the  front  incisors,  between  the  lateral 
incisors  and  canines,  and  between  the  bicuspids.  Adapt  it  to 
the  form  of  the  alveolar  ridge  with  a  hammer  and  pliers,  and 
swage  on  the  plate  along  where  the  teeth  are  to  be  set.  Solder 
up  the  joints  with  pure  gold,  and  proceed  to  back  the  teeth, 
etc.,  as  before ;  making  preparations  for  fastening,  and  remov- 
ing the  slip  of  platina  from  the  gold  plate  before  enveloping 
in  the  investient,  when  proceed  as  before. 

"  When  the  teeth  are  arranged,  insert  four  platina  tubes, 
about  one  line  in  diameter,  two  between  the  molars,  and  two 
between  the  cuspidati  and  bicuspids,  and  solder  to  the  platina 
base.  These  are  designed,  after  the  teeth  are  finished,  to  be 
the  means  of  fastening  to  the  gold  plate,  either  by  riveting  in 
the  usual  way,  or  by  soldering  pins  to  the  gold  plate  passing  up 
through  the  tubes,  fastening  with  sulphur  or  wooden  dowels. 


DENTURES   AYITH   CONTINUOUS   GUMS.  325 

Bv  these  methods  we  are  enabled  to  readily  remove  the  block 
and  repair  it,  should  it  meet  with  any  accident,  and  also,  in 
case  absorption  should  go  on,  to  restrike  the  plate,  or  to 
lengthen  the  teeth.  The  rim  should  be  put  on  the  gold  plate 
after  the  block  is  finished ;  it  gives  great  additional  strength 
and  a  beautiful  finish. 

"  Memoranda. — In  preparing  material  always  grind  dry, 
and  the  most  scrupulous  cleanliness  should  attend  all  of  the 
manipulations.  In  all  cases  where  heat  is  applied  to  an  article 
in  this  system,  it  should  be  raised  gradually  from  the  bottom 
of  the  muffle  and  never  run  into  a  heat.  Where  it  is  desired 
to  lengthen  any  of  the  teeth,  either  incisors  or  masticators,  or 
to  mend  a  broken  tooth,  it  may  be  done  with  covering,  properly 
colored  with  platina,  cobalt,  or  titanium. 

"  In  preparing  a  piece  of  work,  wash  it  with  great  care, 
using  a  stiff  brush  and  pulverized  pumice-stone.  Bake  over  a 
slow  fire  to  expel  all  moisture,  and  wash  again,  when  it  will  be 
ready  for  any  new  application  of  the  enamel.  Absorption, 
occurring  after  a  case  has  been  some  time  worn,  by  allowing 
the  jaws  to  close  nearer,  causes  the  lower  jaw  to  come  forward 
and  drive  the  upper  set  out  of  the  mouth.  By  putting  the 
covering  on  the  grinding  surface  of  the  back  teeth  in  sufficient 
quantities  to  make  up  the  desix'ed  length,  the  coaptation  of  the 
denture  will  be  restored,  and  with  it  the  original  usefulness. 

"  Any  alloy  containing  copper  or  silver  should  not  be  used 
for  solder  or  j)late,  if  it  is  intended  to  fuse  a  gum  over  the 
lingual  side  of  the  teeth,  as  it  will  surely  stain  the  gum. 
Simple  platina  backs  alone  do  not  possess  the  requisite  stiff- 
ness, and  should  always  be  covered  on  platina  with  the  enamel, 
and  on  gold  with  another  gold  back.  In  backing  the  teeth, 
lap  the  backs  or  neatly  join  them  up  as  far  as  the  lower  pin  in 
the  tooth,  and  higher  if  admissible,  and  in  soldering,  be  sure 
to  have  the  joint  so  made  perfectly  .soldered." 

Dr.  IlaakelVs  Methods. 

"It  should  be  borne  in  mind  that  the  strength  of  this  work 
depends  mainly  upon  the  vietaf,  and  not  upon  the  porcelain, 


326  MECHANICAL   DENTISTEY. 

though  the  latter  adds  to  its  strength.  While  platinum  is  a 
very  soft  metal,  yet,  by  means  of  various  devices,  the  plate, 
with  the  teeth  properly  soldered  on,  and  ready  for  the  porce- 
lain, can  be  made  very  stiff  and  strong,  therefore  everything 
that  can  be  done  to  secure  a  strong  foundation  should  be  care- 
fully 'observed. 

"  The  plate  should  be  of  the  best  French  material  (not  re- 
melted  scraps  and  old  plates),  29  to  30  gauge  for  the  upper, 
and  26  to  28  for  the  lower,  and  should  be  swaged  on  Babbitt 
metal  dies.  The  plate  is  then  tried  in  the  mouth,  and  if  the 
fit  is  found  to  be  correct,  arrange  the  articulating  wax,  secure 
the  '  bite,'  and  make  the  articulating  model. 

"  The  back  of  the  plate  should  be  doubled,  for  the  following 
reasons :  It  imparts  increased  strength  ;  leaves  some  margin  for 
change,  in  case  of  necessity,  after  the  work  is  in  the  mouth ; 
protects  the  edge  of  the  porcelain ;  and  admits  of  a  neater 
finish.  This  '  doubler '  should  be  about  three-sixteenths  of  an 
inch  wide,  with  the  edge  turned  up  slightly  to  receive  the 
porcelain.  Around  the  outer  edge,  solder  a  flattened  wire, 
one-sixteenth,  or  less,  of  an  inch  wide,  and  22  gauge,  bringing 
the  ends  to  meet  the  turned  edge  of  the  doubler.  This 
strengthens  the  plate,  and  affords  a  good  round  finish  to  the 
edge,  as  well  as  protection  to  the  porcelain.  This  is  easily  put 
on  after  a  little  practice,  and  is  far  preferable  to  turning  the 
edge  of  the  plate  with  pliers,  or  otherwise.  Pure  gold  should 
always  be  used  for  soldering,  and  with  just  enough  borax 
(using  wevy  little)  to  give  direction  to  the  flow  of  solder. 

"  Then  comes  the  arrangement  of  the  teeth,  and  this  should 
always  be  done  in  the  mouth,  the  articulating  model  being 
only  a  preliminary  guide ;  for  by  the  mouth  alone  can  one  de- 
termine the  correct  expression  and  arrangement  desired ;  and 
it  is  just  here  that  three-fourths  or  more  of  the  artificial  den- 
tures fail  in  an  utter  lack  of  artistic  skill.  In  this  work  there 
is  ample  opportunity  for  the  display  of  taste  and  skill,  so  that 
perfection  itself  is  attained  at  the  hands  of  the  true  artist. 

"  The  investing  process  comes  next.  First,  a  coat  of  shellac 
over  the  teeth  to  prevent  etching  (although  if  this  occurs,  it  is 


DENTURES    AVITH    CONTINUOUS   GUMS.  327 

not  a  matter  of  much  account,  as  the  baking  remedies  it). 
Then  a  thin  coat  of  clear  plaster;  next  plaster  and  asbestos, 
one  part  of  the  latter  to  two  of  the  former.  Let  the  portion 
under  the  plate  extend  at  least  one  inch  back  of  the  latter,  as 
this  bottom  portion  is  to  be  retained  to  bake  the  case  on  ;  in- 
vest the  whole  one-half  inch  thick.  Warm  the  case  until  the 
plate  is  sufficiently  heated  to  remove  the  wax  easily;  dash 
boiling  water  over  it  (this  is  the  best  method  to  remove  wax 
adhering  to  teeth  and  plate  in  all  kinds  of  work).  The  back- 
ings should  be  continuous,  and  be  lapped  on  to  the  plate,  for 
in  this  is  the  main  stay  of  the  work  for  strength.  Cut  patterns 
in  tin  or  lead,  three  pieces,  one  for  the  six  front  teeth,  and  one 
for  each  side,  lapping  over  the  eye-teeth ;  the  foot-piece  should 
lap  on  to  the  plate  about  three-sixteenths  of  an  inch.  No 
borax  is  needed.  The  gold  should  be  melted  and  rolled  into 
a  ribbon  as  thin  as  possible,  and  cut  in  small  pieces  and  laid 
under  the  lap,  or  foot-piece,  and  a  piece  under  each  pin.  The 
backings  can  be  fitted  more  easily  by  slitting  the  foot-piece. 
The  most  convenient  method  of  soldering  is  in  the  furnace, 
being  careful  not  to  let  it  remain  too  long,  so  as  to  fuse  the 
enamel  on  the  teeth.  If  a  pin  should  fail  to  solder,  it  is  not 
material,  as  the  '  body '  will  hold  it. 

"  After  cooling,  remove  the  plaster,  and  save  the  base.  If 
any  teeth  are  etched,  sandpaper  them  and  remove  every  par- 
ticle of  plaster ;  with  a  sharp  instrument  scarify  the  surface 
of  the  plate.  Place  the  plate  on  the  articulating  model,  and  if 
it  is  sprung,  press  it  into  place,  which  is  very  readily  done. 

"The  '  body,'  and  enamel  or  gum  color,  as  prepared  by  S. 
L.  Close,  is  the  only  reliable  material  to  be  had,  as  Dr.  Allen 
no  longer  furnishes  it  for  the  trade.  Apply  the  '  body '  mixed 
with  water,  quite  thin,  by  means  of  an  oval-pointed  knife,  oc- 
casionally jarring  with  handle  of  spatula,  and  as  the  moisture 
comes  to  the  surface,  absorb  with  a  cloth  ;  after  it  is  well  filled 
into  all  interstices,  apj)ly  it  thicker,  jarring,  absorbing,  and 
j)acking  hard,  until  enough  is  on  the  outside  to  produce  the 
proper  shape  and  contour  of  the  lips.  Then  ap})ly,  with  the 
curved  point  of  knife,  the  body  to  the  lingual  side  of  the  plate, 


328  MECHANICAL   DENTISTRY. 

same  as  on  the  outside,  but  only  a  thin  coat  on  the  plate. 
Trim  around  the  necks  of  the  teeth,  remove  all  particles  from 
between  with  a  quill  toothpick,  and  brush  all  particles  off  the 
surface  of  the  teeth  and  exposed  portions  of  plate,  and  the  case 
is  ready  for  baking. 

"  The  Philadelphia  furnace,  sold  by  all  dealers  in  dental 
goods,  we  prefer.  It  is  always  best  to  use  the  largest  size,  No. 
1,  yet  No.  2  will  do  if  the  larger  size  cannot  be  had.  Be  sure 
of  a  good  draught.  The  furnace  can  be  used  as  it  comes ;  a 
better  plan  is  to  knock  the  bottom  out  of  the  lower  section, 
get  longer  bars,  that  will  extend  some  distance  through  the 
front,  the  two  centre  ones  at  least  18  inches.  Build  a  hearth, 
two  bricks  thick  and  three  feet  square ;  build  an  inclosure  of 
brick,  about  12  inches  high,  large  enough  to  set  the  furnace  on, 
and  line  with  fire-brick.  Provide  a  sheet-iron  cover  for  the 
front  to  close  the  draught. 

"  In  setting  the  '  muffle,'  see  that  the  vent-hole  in  the  top 
is  clear ;  this  is  for  escape  of  gas  that  may  be  in  the  muffle, 
and  would  injure  the  work.  Fasten  the  front  end  with  fire- 
clay, but  leave  the  back  end  free. 

"  The  fuel  to  be  used  must  be  anthracite  coal,  or  else  coke ; 
Lehigh,  range  size,  is  the  best. 

"  A  sheet-iron  shelf,  the  edge  bent  into  the  space  between 
the  furnace  and  cover,  and  with  a  leg  riveted  to  it  and  resting 
on  the  long  bars,  is  needed  to  set  the  case  on,  to  heat  up  and 
run  into  the  muffle  gradually.  Set  the  case  ten  or  twelve 
inches  from  the  opening,  move  forward,  every  ten  or  fifteen 
minutes,  a  couple  of  inches,  until  it  is  in  the  muffle ;  ])lace  it 
within  two  inches  of  the  back,  and  close  the  door.  If  the  heat 
is  right,  five  or  ten  minutes  will  suffice  ;  still  it  must  be  looked 
at  so  as  not  to  get  too  much  heat.  This  first  bake  should  be 
only  a  glaze.  Remove  to  a  muffle  on  the  hearth,  and  close  up 
tight.  When  cool,  place  on  the  model,  and,  if  sprung,  press 
it  into  place.  Next  fill  up  all  the  cracks  with  very  thin  body, 
jarring  with  handle  of  the  spatula  often,  so  that  the  material 
will  fill  up  thoroughly ;  then  spread  on  thicker  until  the  proper 
shape  and  fulness  are  secured,  trimming  around  the  teeth,  and 


DENTURES   WITH    CONTINUOUS    GUMS.  329 

doing  as  previously  described,  and  bake  as  before,  only  more 
so  ;  it  should  be  ghssy.  After  cooling,  the  enamel  is  to  be  put 
on  the  same  as  the  body,  applying  only  a  thin  and  uniform 
coat.  The  rugae  can  be  produced  in  the  body  or  in  the  gum.  The 
enamel  should  have  a  thoroughly  glossy  appearance  when 
ready  to  remove  from  the  furnace.  Heated  cooling  muffles 
are  unnecessary,  as  the  case  itself  will  heat  the  muffle  all  that 
is  necessary. 

"  Lower  sets  are  better  without  a  binding,  as  it  is  sometimes 
necessary  to  file  or  grind  away  the  edge.  Use  plate  No.  8,  or 
even  thicker,  and  solder  on  the  edge  a  narrow  strip,  ^«^ 

"  The  case  is  finished  by  filing  and  polishing  the  exposed 
metal  surface,  not  doing  anything  to  the  upper  surface. 

"A  'defined'  air-chamber  is  rarely  necessary, — a  Cleveland 
chamber,  never.  Raise  the  plate  over  the  hard  palate  with  a 
thin  film  of  wax  on  the  plaster  cast,  chamfering  off  the  edges 
completely ;  scrape  the  plaster  model  across  the  back,  except 
right  in  the  centre,  according  to  the  softness  of  the  palate. 

"This  work  is  not  advisable  for  partial  sets,  except  in  some 
partial  lower  cases  where  there  are  no  detached  teeth.  In  these 
cases,  the  plate  should  be  at  least  two  thicknesses  across  the 
back  of  the  front  teeth,  and  resting  well  up  on  the  necks  of 
the  same. 

"  Very  few  seem  to  know  how  to  prepare  a  case  for  repair- 
ing. Invest  it  in  plaster  and  asbestos  at  least  one-half  of  an 
inch  deep  entirely  ;  place  in  the  muffle  before  lighting  the  fire, 
and  allow  it  to  remain  witii  the  door  open,  as  the  fire  comes 
up,  until  it  is  red  hot ;  then  remove,  cool,  and  clean  off  the 
plaster  thoroughly,  preserving  the  base,  and  it  can  be  run  into 
the  furnace  with  as  little  danger  of  cracking  as'  if  it  had  never 
been  worn. 

"Grind  out  the  remains  of  the  teeth  below  the  margins  of 
the  gum  ;  select  a  rubber  tooth,  as  it  is  easier  to  get  and  just  as 
good  as  one  made  for  tliis  work,  filing  off  the  pins;  hold  with 
wax  until  a  little  })la.ster  and  asbestos  can  be  placed  over  it 
and  the  adjoining  teeth  ;  remove  the  wax  thoroughly  and  put 


330  MECHANICAL   DENTISTRY. 

on  repairing  body,  and  bake ;  cool,  put  on  the  gum,  having 
previously  ground  off  a  portion  of  the  old  gum  if  it  is  a  very 
old  ease,  and  put  on  just  a  little  new,  and  bake  as  at  first. 

"  If  blisters  occur,  grind  into  them  and  fi:ll  with  body  and 
gum,  three  to  one,  press  hard,  and  enamel." 

Dr.  Field's  Methods. 

"  When  the  platinum  has  once  touched  the  metal  dies,  never 
place  it  under  the  blowpipe  without  its  having  been  thoroughly 
pickled.  This  is  often  neglected,  and  the  consequence  is  that 
the  plate  will  become  more  or  less  discolored  from  the  absorp- 
tion, under  heat,  of  the  baser  metal  into  the  platinum.  When 
the  teeth  are  properly  arranged  with  wax  on  the  plate,  as  di- 
rected by  Dr.  Allen,  invest,  but  use  no  sand,  simply  plaster 
and  asbestos.     My  reason  for  this  I  will  give  further  on. 

"After  the  investment  has  become  sufficiently  hard  to  han- 
dle, the  backings  may  be  adjusted,  and  here  I  shall  differ  some- 
what with  Dr.  Allen,  for,  instead  of  the  continuous  backing,  I 
back  each  tooth  separately,  and  for  two  reasons,  one  of  which 
is,  that  I  think  my  job  will  be  stronger  when  completed,  by 
allowing  the  body  to  be  well  worked  in  between,  below,  and 
completely  around  the  teeth  without  a  platinum  wall,  as  it 
were,  separating  the  body  on  a  line  running  completely  around 
the  alveolar  ridge,  and  only  just  touching  over  the  top  of  this 
platinum. 

"My  second  reason  is  that,  should  the  teeth  be  drawn 
out  of  place  any,  as  they  are  sometimes  by  the  investings 
cracking  and  pulling  away  from  the  plate,  the  single  backing 
of  each  tooth  admits  of  a  much  easier  and  more  perfect  re- 
adjustment than  when  the  backing  is  continuous.  Make  the 
backings  of  a  somewhat  V  shape,  that  is,  let  them  be  a  little 
narrower  at  the  top  than  where  they  come  in  contact  with  the 
plate ;  bend  up  the  lower  part  of  the  backing  to  the  extent  of 
about  one-sixteenth  of  an  inch,  and  at  such  an  angle  that  when 
placed  in  position  behind  the  platinum  pin,  to  which  it  is  to 
be  soldered,  it  shall  fit  fairly  and  squarely  on  the  plate ;  put 
in  position  and  press  down  your  pin  on  it,  first  having  placed 


DENTURES   WITH    CONTINUOUS   GUMS.  331 

a  piece  of,  say  number  20,  gold  foil,  folded  two  or  three  times 
on  itself,  one-sixteenth  of  an  inch  square,  against  the  backing, 
so  that  when  the  pin  is  bent  down  upon  it,  it  shall  hold  it 
from  slipping  away;  then  with  a  pair  of  ordinary  plugging 
pliers  squeeze  the  foil  up  to  and  around  the  pin;  then  place 
one  or  two  pieces  of  solder  (pure  gold)  just  behind,  and  close 
against,  the  heel  of  the  foot-shaped  backing.  By  placing  it 
here,  the  danger  of  it  slipping  away  when  the  borax  calcines 
under  heat  is  a%'oided.  The  less  solder  you  use,  and  still  have 
your  teeth  fastened,  the  better,  for  the  reason  that  the  gold 
flowing  at  a  less  heat  than  that  required  for  the  fusing  of  the 
body,  the  gold  is  in  a  state  of  fusion  ichen  the  body  has  set,  and 
there  will  be  no  adhesion  between  the  gold  and  the  body.  Now 
solder  as  most  convenient.  I  find  the  Fletcher  furnace  an  ad- 
mirable contrivance  for  this  purpose,  ten  minutes  being  all  the 
time  necessary  to  complete  the  work.  Remove  the  investing 
carefully,  and  presei've  it  all  for  future  use.  The  plate  is  then 
tried  in  the  mouth,  and  the  teeth  nicely  adjusted  to  those  with 
which  they  are  to  antagonize. 

''  Everything  is  now  ready  for  the  first  baking.  Pour  out 
upon  a  clean  butter  plate  the  amount  of  body  required,  into 
which  pour  sufficient  pure  water  to  make  a  thin  paste,  and  then 
begin  the  work  of  moulding  and  carving  your  job  by  filling 
in  between  and  under  all  the  teeth,  tapping  your  plate  gently 
from  time  to  time ;  this  will  bring  the  water  to  the  surface  and 
settle  the  body  into  every  nook  and  crevice.  After  each  tap- 
ping, absorb  the  surface  water  with  a  clean  napkin  ;  by  so 
doing,  you  will  the  better  hold  the  body  to  its  place,  and  pre- 
vent its  running  where  not  wanted.  Build  over  the  roots  of 
the  incisors  and  cuspids  boldly,  leaving  a  corresponding  de- 
pression between  the  teeth;  thus,  when  the  piece  is  completed, 
you  will  have  that  natural  and  lifelike  appearance  as  of  the 
roots  of  the  teeth  showing  slightly  through  the  gum. 

"  Xow  take  that  part  of  your  investing  material  that  cov- 
ered the  teeth  when  the  piece  was  soldered,  and  grind  up  fine, 
and  with  it  make  a  cushion  on  the  slab  that  is  to  hold  the  case 
in  the  furnace.     This  cushion  should  be  about  one-fourth  of 


332  MECHANICAL   DENTISTRY. 

an  inch  thick ;  then  place  your  piece  on  this  base,  teeth  down- 
wards, and  take  a  small  spatula  and  work  the  powdered  ma- 
terial well  up  against  the  teeth,  so  that  the  bearing  shall  be 
equal  under  every  tooth ;  this,  if  properly  done,  will  prevent 
any  dravnng  aioay  of  the  teeth  from  their  proper  position,  as 
is  frequently  the  case  when  the  plate  is  placed  in  the  muiSe 
with  the  teeth  upwards,  the  cause  being  the  shrinkage  of  the 
body ;  and  now  comes  my  reason  for  not  using  sand  in  this  in- 
vesting material,  viz.,  the  sand  acting  as  a  flux  would  attach 
itself  more  or  less  to  the  teeth  themselves,  and  I  have  seen  this 
thing  carried  so  far,  when  the  heat  was  a  little  too  high,  as  to 
solidly  fuse  teeth  and  slab  together. 

"  The  piece  is  now  ready  for  the  first  baking,  and  this  should 
be  carried  no  farther  than  to  shrink  the  body  as  much  as  pos- 
sible, not  going  beyond  a  semi-fuse.  After  this  is  completed, 
and  the  case  cooled,  proceed  to  fill  up  all  cracks  and  shrinkage 
by  the  application  of  more  body,  when  the  case  is  ready  for 
the  second  baking.  This  should  be  done  with  the  plate  re- 
versed, teeth  upwards,  using  for  a  support  that  part  of  the 
investing  which  came  in  contact  with  the  platinum,  and  which 
should  be  preserved  unbroken.  In  this  second  baking  of  the 
body,  care  should  be  taken  that  it  be  not  overdone.  A  piece 
properly  baked  will  present  a  beautifully  granulated  appear- 
ance, the  tips  of  the  granules  sparkling  like  little  dewdrops. 
Carrying  the  heat  beyond  the  stage  necessary  to  produce  this 
effect,  vitrifies  the  body,  thereby  very  much  lessening  the 
strength  of  the  work  when  completed. 

"  If  now  it  is  found  that  a  third  body  is  not  required  (and 
it  rarely  is  if  proper  care  has  1  een  taken  with  the  work  so  far, 
although  occasionally  it  may  be  necessary)  proceed  with  the 
enamelling  as  directed  by  Dr.  Allen.  Should  there  be  any 
little  rough  spots  on  the  teeth,  caused  by  overheating  when 
soldering,  paint  them  over  with  a  little  clean  pulverized  borax 
mixed  with  water ;  this  will  flow  the  tooth  enamel,  and  cause 
them  to  come  out  from  the  mufile  as  bright  and  smooth  as 
when  they  first  left  the  factory. 

"The  work  is  now  ready  for  its  third  and  final  baking, 


DENTURES   WITH   CONTINUOUS   GUMS.  333 

which  should  be  with  a  quick,  sharp  fire.  When  fused,  draw 
to  the  front  part  of  the  muffle;  put  in  the  muffle  pUig,  and 
then  dump  the  fire,  and  leave  until  tlie  furnace  is  cold  ;  by  so 
doing,  the  case  is  well  annealed,  and  all  danger  of  checking 
the  enamel  avoided.  Twenty  or  thirty  minutes  now  are  all 
that  are  necessary  for  what  little  finishing  the  plate  will  require, 
when  it  will  be  ready  for  the  mouth. 

"  Let  it  be  remembered  by  the  beginner  tliat  on  the  carving 
of  the  first  body  largely  depends  the  artistic  beauty  of  the  work. 
Keep  your  patient's  face  well  before  you  in  your  mind's-eye, 
and  reproduce  in  the  porcelain  all  those  little  minor  details 
which,  when  properly  arranged  and  blended  together,  shall  so 
counterfeit  nature's  handiwork  that  that  of  man's  can  hardly 
be  detected." 

Application  of  Continuous  Gum  to  Partial  Sets. — The  fol- 
lowing method  of  constructing  partial  sets  of  artificial  teeth 
with  continuous  gum  is  taken  from  a  practical  and  well-written 
paper  on  this  process  by  Dr.  W.  B.  Roberts : 

"  Partial  cases  may  be  made  of  continuous  gum ;  but  the 
work  is  so  various  in  its  nature,  that  the  dentist  must  neces- 
sarily depend  much  upon  his  own  judgment.  Difficult  cases 
will  constantly  present  themselves,  that  will  require  the  exer- 
cise of  much  study  and  ingenuity ;  in  which  the  general  instruc- 
tion that  can  be  given  in  words,  may  be  of  but  little  service. 
The  first  attempt  of  this  kind  in  my  own  experience,  was  in 
replacing  two  central  incisors.  Taking  two  continuous  gum 
teeth,  I  placed  upon  them  a  platinum  lining,  slitting  this  down 
along  the  edge  of  one  tooth  nearly  through  the  piece  and  up 
the  edge  of  the  other  tooth  by  a  parallel  cut,  leaving  the  two 
parts  joined  together  by  a  narrow  slip.  This  allowed  sufficient 
motion  between  the  teeth,  so  that  they  could  be  adjusted  as 
desired.  I  then  placed  a  bit  of  tissue-paper  on  the  plaster 
mcxlel,  covering  the  spot  to  be  occupied  by  the  teeth  and  gum, 
to  i)revent  the  adhesion  of  the  body  to  the  plaster,  and  holding 
the  two  incisors  in  their  j)laces,  I  worked  the  body  into  all 
the  depressions  of  the  gtim  and  around  the  roots  of  the  teeth. 
I  then  removed  the  whole  from  the  model,  and  pUu-ctl  the 


334  MECHANICAL   DENTISTEY. 

piece  in  a  paste  of  pulverized  silex,  or  plaster  and  asbestos, 
upon  a  slide,  and  baked  as  described  for  full  sets.  The  little 
slip  of  platinum  kept  the  two  teeth  in  place.  The  work  shrunk 
somewhat ;  but  this  was  remedied  by  again  placing  the  piece 
upon  the  model  with  the  intervention  of  tissue-paper  covered 
with  a  thin  coating  of  body.  Into  this  I  pressed  the  piece, 
till  it  occupied  its  true  place,  and  then  filled  in  again  with 
more  body  all  the  crevices  around  the  roots  of  the  teeth,  and 
rebaked. 

"  After  enamelling,  if  the  work  has  been  carefully  and  skil- 
fully done  upon  this  plan,  it  will  be  as  fine  a  piece  in  appear- 
ance and  fit,  as  can  be  made.  It  may  then  be  soldered  to  a 
gold  plate,  and  the  little  strip  of  platinum  between  the  teeth 
be  cut  out.  With  the  body  and  gum  formerly  in  use  many 
difficulties  were  often  encountered  from  discoloration  of  the 
gum,  or  from  other  injuries  incurred  in  soldering.  But  with 
Roberts's  material,  these  are  easily  avoided,  and  the  piece  can 
be  treated  the  same  as  a  block  or  single  gum  teeth.  In  par- 
tial sets  on  entire  plates  of  platinum,  I  have  sometimes  found 
trouble,  from  the  enamel  giving  way  upon  the  small  narrow 
points  that  connect  the  teeth  with  the  plate,  by  the  shock  occa- 
sioned in  biting.  I  have  consequently  left  these  points  un- 
covered, and  used  two  or  three  thicknesses  of  platinum  to  give 
greater  strength.  But  where  this  is  likely  to  occur,  gold  plates 
would  be  preferable,  if  nicely  adapted  with  single  gum  teeth, 
or  blocks  of  continuous  gum,  as  the  case  might  require.  I 
have  also  applied  continuous  gum  in  cases  where  the  natural 
teeth,  from  one  to  five  in  number,  were  left  in  the  mouth,  by 
making  the  plates  as  in  full  sets,  cutting  out  around  the  natural 
ones,  and  raising  a  small  bead,  or  placing  a  light  wire  around, 
about  one-eighth  of  an  inch  or  more  from  the  teeth,  against 
which  the  gum  or  body  is  to  be  finished.  The  points  around 
the  teeth  are  to  be  left  free,  in  order  to  be  burnished  down  in 
case  of  imperfections  caused  by  the  difficulty  of  obtaining  exact 
impressions  in  these  places.  In  such  cases  I  have  sometimes 
formed  a  strong  standard  of  several  thicknesses  of  platinum 
fitting  closely  against  one  or  more  natural  teeth,  leaving  a 


DENTURES   WITH    CONTINUOUS    GUMS.  335 

loophole  through  which  to  run  a  gold   clasp  for  afterward 
securing  the  artificial  set. 

"I  have  also  secured  the  gold  to  the  standard  by  rivets  of 
platinum,  and  sometimes  by  two  or  three  gold  screws,  not  pro- 
viding, in  these  cases,  the  loophole.  These  methods  are  to  be 
preferred  to  using  solder  for  fastening  ;  for,  in  case  of  repair, 
the  clasps  are  easily  removed  without  leaving  any  foreign  subr 
stance ;  but  in  case  of  soldering,  however  carefully  they  may 
be  removed,  there  will  remain  some  alloy,  which  in  the  baking 
heat  to  which  the  piece  is  to  be  exposed,  will  be  incorporated 
with  the  platinum.  Even  so  small  an  amount  of  silver  as  may  be 
in  gold  coin  used  for  solder  will  communicate  a  yellowish  tinge 
to  the  gum,  spoiling  the  whole  work.  Many  operators  in  their 
early  practice,  I  doubt  not,  experienced  this  result ;  and  learned 
that  no  alloys,  especially  of  silver  or  copper,  can  be  admissible 
for  soldering  this  work.  I  have  tried  platinum  clasps  without 
success,  as  no  elasticity  could  be  obtained,  and  therefore  would 
not  hold  upon  the  teeth.  Another  source  of  mischief  may 
properly  be  noticed  in  this  place.  In  baking,  especially  with 
a  new  furnace,  or  with  muffles  lately  renewed,  either  at  the 
first  or  second  heat,  or  it  may  be  in  enamelling,  the  piece  is 
sometimes  changed  in  its  texture  and  color,  as  is  supposed  by 
tlie  gases  present,  and  the  phenomenon  is  called  gassing  the 
piece.  The  body  becomes  porous  like  honeycomb,  and  of  a 
bluish  color.  When  this  occurs  there  is  no  remedy  but  to 
place  it  on  the  metallic  die,  remove  the  whole  of  the  injured 
part,  and  replace  it  with  a  new  coating  of  body  and  gum.  The 
teeth  are  seldom,  if  ever,  thus  affected.  As  a  precaution,  the 
muffles  should  be  well  ventilated  with  holes  for  the  passage  of 
tlie  heated  air  and  gases," 


336  MECHANICAL   DENTISTRY. 


CHAPTER  XIV. 
Vulcanite  Base. 

While  there  are  undoubtedly  many  important  uses  to  which 
vulcanized  india-rubber  may  be  applied  in  the  practical  depart- 
ments of  dentistry,  and  for  which  it  would  be  difficult  to  find 
an  adequate  substitute,  yet  there  are  accumulating  evidences 
leading  to  the  conclusion  that  its  total  abandonment,  as  a  base 
for  artificial  dentures,  by  intelligent  and  conscientious  prac- 
titioners everywhere  is  an  event  of  the  near  future. 

This  anticipated  result,  in  respect  to  a  material  which  has 
been  almost  universally  employed  as  a  base  for  the  past  twenty 
years,  is  assured  by  the  confirmed  and  steadily  increasing  dis- 
trust of  its  suitableness  for  the  purpose  indicated,  and  the  grow- 
ing tendency  in  the  profession  to  return  to  higher  and  less 
objectionable  forms  of  substitution  as  respects  both  material  and 
construction. 

While  what  has  heretofore  been  stated  in  regard  to  rubber 
as  a  base  in  former  editions  of  this  work  reflected,  as  the  author 
then  believed,  the  estimate  of  its  fitness  by  the  profession  gen- 
erally, so,  it  is  believed,  does  what  is  now  written  embody  the 
present  judgment  of  the  mass  of  enlightened  practitioners  in 
reference  to  its  unsuitableness  and  the  necessity  of  its  abandon- 
ment as  a  base.  That  the  latter  is  a  consummation  "  devoutly  to 
be  wished,"  and  that  it  would  be  in  the  interests  not  only  of  the 
profession  but  of  all  concerned,  is  scarcel}^any  longer  a  disputed 
question,  and  should  the  present  work  ever  reach  another  edition, 
the  author  hopes  to  find  in  a  still  more  advanced  professional 
and  public  sentiment  authority  for  classifying  it,  as  a  base, 
among  the  obsolete  methods  of  substitution. 

General  Properties  of  India-rubber. — Caoutchouc,  gum-elastic 
or  india-rubber,  exists  as  a  milky  juice  in  several  plants,  but 


VULCANITE   BASE,  337 

is  extracted  chiefly  from  the  Siphonia  cahuca,  which  grows  in 
South  America  and  Java.  It  is  discharged  through  numerous 
incisions  made  in  the  tree  through  the  bark,  and  is  spread  upon 
clay  moulds,  and  dried  in  the  sun,  or  with  the  smoke  of  a  fire, 
which  blackens  it.  The  juice  when  first  obtained  is  of  a  pale 
yellow  color,  of  about  the  consistence  of  cream,  and  has  a  specific 
gravity  of  about  1.012.  In  the  process  of  drying,  55  per  cent, 
is  lost,  the  residuary  45  being  elastic  gum.  It  immediately 
coagulates,  by  reason  of  its  albumen,  on  the  application  of  heat, 
the  elastic  gum  rising  to  the  surface.  The  specific  gravity  of 
the  juice  is  diminished  by  inspissation,  becoming  0.925  when 
hard,  and  cannot  be  permanently  increased  by  any  degree  of 
pressure.  When  once  stiffened  by  cold,  or  continued  quies- 
cence, it  cannot  be  restored  to  its  original  condition  of  juiciness. 
The  inspissated  juice,  or  crude  rubber  of  commerce,  is  alto- 
gether insoluble  in  water  or  alcohol,  but  is  readily  soluble  in 
ether  deprived  of  its  alcohol  by  washing,  affording  a  colorless 
solution.  On  evaporation  of  the  ether,  the  gum  resumes  its 
original  condition.  It  swells  to  thirty  times  its  bulk  when 
treated  with  hot  naphtha,  and  if  triturated  in  this  condition  in 
a  mortar,  and  pressed  through  a  sieve,  furnishes  a  homogeneous 
varnish  employed  in  the  preparation  of  a  waterproof  cloth. 

Caoutchouc  is  solul)le  in  the  fixed  oils,  but  is  not  readily 
decomposed  by  cold  sulphuric  acid  or  diluted  nitric  acid,  and  is 
unaffected  by  either  muriatic  acid  gas,  sulphurous  acid  gas,  fluo- 
silicic  acid,  ammonia  or  chlorine,  nor  is  it  dissolved  by  the 
strongest  caustic  potash  lye,  even  at  a  boiling  heat,  and  is  there- 
fore highly  esteemed  as  an  appliance  of  the  chemical  laboratory. 
According  to  the  experiments  of  Ure,  Faraday,  and  others,  caout- 
chouc contains  no  oxygen,  as  almost  all  other  solid  vegetable 
products  do,  but  is  a  mere  compound  of  carbon  and  hydrogen, 
in  the  proportion  of  three  atoms  of  the  former  to  two  of  the 
latter.  From  its  proi)crty  of  resisting  the  corrosive  action  of 
ar-id  vapjrs,  and  its  tenacity  of  adhesion  to  glass,  caoutchouc, 
whea  melte<l,  forms  a  very  excellent  lute  for  chemical  apjiarata. 
Such  are  some  of  the  properties  of  this  remarkable  product, 
the  uses  of  which  have  been  almost  immeasurably  extended 

22 


338  MECHANICAL  DENTISTRY. 

since  the  first  successful  efforts  to  produce  artificial  induration 
by  Charles  Goodyear  in  1844. 

Compounding  Rubber  for  Dental  Purposes. — India-rubber 
is  prepared  for  vulcanizing  by  incorporating  with  it,  in  vary- 
ing proportions,  either  sulphur  alone  or  some  of  its  compounds, 
sulphur  being  an  essential  component  of  all  vulcanizable  gum 
compounds.  For  dental  purposes,  the  coloring  is  effected  in 
most  preparations  by  the  introduction  of  vermilion  (sulphuret 
of  mercury).  These  substances,  properly  combined,  are  sub- 
jected to  artificial  heat  for  a  specified  time,,  producing  a  hard, 
elastic,  hornlike  substance,  possessing  the  qualities  of  lightness, 
strength,  durability,  imperviousness  to  fluids,  insolubility  in  the 
oral  secretions,  unchangeableness  in  exposure  to  ordinary  tem- 
peratures, etc. 

Method  of  Constructing  an  Entire  Denture  in  a  Base  of  Rub- 
ber.— As  the  manipulations  concerned  in  the  construction  of  a 
full  upper  set  differ  in  no  essential  respect  from  those  required 
in  the  formation  of  a  denture  for  the  inferior  arch,  except  as 
the  two  differ  in  conformation,  requiring  corresponding  modifi- 
cations of  practice  which  will  readily  suggest  themselves,  it 
will  be  sufficient  to  describe  the  method  of  constructing  an  en- 
tire denture  for  the  upper  jaw. 

An  impression  of  the  mouth  is  first  secured  in  the  usual 
manner,  and,  for  full  sets,  plaster  of  Paris  is  preferable  to  any 
other  material  for  the  purpose.  In  all  practicable  cases  the 
same  substance  may  be  employed  in  cases  of  partial  pieces. 
As  rubber,^  when  rendered  plastic  by  heat  and  subjected  to 
pressure,  receives  a  distinct  and  perfect  impress  of  the  face  of 
the  model,  it  is  important  that  the  latter  should  be  as  smooth 
upon  its  surface,  and  as  free  from  faultiness  of  form  or  surface 
blemish  as  possible.  From  the  impression  a  plaster  model  is- 
obtained,  and  if  an  air-chamber  is  required,  it  may  be  secured 
either  by  cutting  out  from  the  impression  before  filling  in  with 
plaster  for  the  model,  or  it  may  be  raised  upon  the  model  after 
the  latter  has  been  separated  from  the  impression.  F04'  the 
latter  purpose,  lead  is  often  used,  but  sheet  tin,  cut  to  the  re- 


VULCANITE   BASE.  339 

quired  form,  is  preferable,  as  the  former  leaves  a  tenacious  coat- 
ing of  oxide  adhering  to  the  plate. 

A  temporary  or  model  base  plate  is  next  conformed  as  ac- 
curately as  possible  to  the  face  of  the  model,  and  for  this  pur- 
pose the  prepared  gutta-percha  is  the  best,  though  sheet  wax 
may  be  used.  The  former  may  be  softened  either  by  sub- 
jecting it  to  a  dry  heat  until  sufficiently  plastic,  or  by  im- 
mersing it  in  hot  water.  The  face  of  the  model  being  pre- 
viously well  saturated  with  cold  water  to  prevent  the  wax 
or  gutta-percha  from  adhering,  the  latter  is  pressed  or  moulded 
accurately  to  the  model  with  the  fingers  moistened  with  cold 
water,  heating  such  portions  from  time  to  time  as  do  not 
readily  yield  to  pressure  until  an  accurate  adaptation  of  all 
portions  of  the  plate  is  secured ;  then  trim  to  the  required  di- 
mensions. 

Having  fitted  the  temporary  plate  to  the  model,  it  is  placed 
in  the  mouth  with  a  wax  guide  or  rim  attached,  when  the 
latter  is  trimmed  to  the  required  width,  fulness,  and  contour, 
and  the  "  bite  "  of  the  under  teeth  secured ;  it  is  then  removed 
and  placed  in  its  proper  position  on  the  model,  and  the  heel  of 
the  latter  extended  an  inch  or  more  posteriorly  to  form  an 
articulating;  surface  for  the  remaining;  section  of  the  antagoniz- 
ing  model,  the  latter  being  obtained  in  the  manner  described 
in  connection  with  metallic  plate  base.  The  mode  of  proced- 
ure in  case  of  entire  dentures  for  the  upper  and  lower  jaws 
differs  in  no  respect  from  that  practiced  when  gold  or  other 
metallic  plate  is  used  as  a  base. 

Arranging  the  Teeth. — Having  secured  an  antagonizing 
model,  the  teeth  are  selected  and  arranged  upon  the  temporary 
gutta-percha  plate  in  the  usual  manner.  The  porcelain  teeth 
used  in  this  process  are  more  commonly  in  the  form  of  blocks 
or  sections,  although  either  single  gum  or  plate  teeth  may  be 
employed.  Preference  is  given  to  the  former,  because  a  fewer 
number  of  seams  or  joints  arc  presented  for  the  intrusion  of 
rubber,  which,  though  forming  ever  so  minute  a  line  of  sepa- 
ration, mars  the  beauty  of  the  finished  work  by  an  unsightly 
contrast  in  color  with  the  porcelain   gum,  and  which  is  not 


340  MECHANICAL   DENTISTEY. 

always  possible  entirely  to  exclude.  The  increased  strength 
of  attachment  formed  by  the  greater  number  of  pins  also  ren- 
ders them  more  permanent  and  enduring  than  single  teeth. 
Teeth  made  expressly  for  rubber  base  were  originally  manu- 
factured with  plain  platina  pins,  longer  and  heavier  than  those 
used  in  connection  with  metallic  plates  (Fig.  126);  these, 
when  used,  were  curved  and  pressed  together,  forming  loops 
or  hooks  to  prevent  them  withdrawing  from  the  rubber.  Sub- 
sequently, however,  the  detachment  of  the  teeth  was  more 
securely  and  certainly  provided  against  by  the  substitution  of 
headed  pins  (Fig.  127),  which  rendered  their  withdrawal  from 
the  rubber  impossible.     For  this  valuable  improvement  the 

Fig.  126.  Fig.  127. 


profession  is  indebted  to  the  late  Dr.  S.  S.  White,  whose  genius, 
enterprise,  and  intelligence  Avere  so  long  and  unceasingly  tribu- 
tary to  the  needs  of  the  dental  practitioner. 

In  arranging  the  teeth,  portions  of  the  wax  rim  are  cut 
away  to  form  a  bed  for  each  tooth  or  block,  as  the  case  may 
be,  grinding  from  the  base  of  the  latter  and  from  their  proxi- 
mate edges  until  the  proper  position  is  assigned  to  the  teeth, 
and  the  required  antagonism  is  secured.  The  teeth,  whether 
single  or  in  the  form  of  blocks,  should  be  united  to  each  other 
laterally  with  the  greatest  possible  accuracy  to  prevent,  as  far 
as  practicable,  the  intrusion  of  the  gum  material  between  them. 
To  further  provide  against  this,  various  expedients  have  been 
resorted  to  with  the  view  of  cementing  or  packing  the  joints  in 
order  to  render  them  impervious  to  the  rubber.  The  sub- 
stances usually  recommended  for  this  purpose  are,  plaster  or 
finely  pulverized  silex  or  felspar  moistened  with  dilute  liquid 
silex ;  os-artificial ;  soluble  glass ;  gold  or  tin  foil,  or  fusible 
metal  packed  into  the  joints,  etc.     Of  the  more  destructible 


VULCANITE   BASE.  341 

substances  mentioned,  Professor  Wildman  very  justly  ob- 
serves :*  "  All  of  these,  in  course  of  time,  will  yield  to  the 
action  of  the  fluids  of  the  mouth  ;  and  then  the  ill-fitted  joints 
will  be  receptacles  for  soft  particles  of  food,  which  will  be 
more  objectionable  than  having  them  filled  with  good  solid 
rubber.  The  best  filling  is  an  accurately  fitted  joint ;  when  so 
made,  if  the  enveloping  plaster  is  of  good  quality  and  properly 
mixed,  and  no  undue  force  is  used  in  bringing  the  section  of 
the  flask  together,  there  is  little  danger  of  the  rubber  insinuat- 
ing itself  into  the  joints."  As  properly  remarked,  there  is  no 
expedient  which  will  so  certainly  and  effectually  exclude  the 
rubber  as  close-fitting  joints,  and  if  the  precaution  is  taken  to 
secure  an  accurate  and  uniform  coaptation  of  the  ground  sur- 
faces where  they  unite  in  front,  and  the  "  enveloping  plaster  is 
of  good  quality  and  properly  mixed,  and  no  undue  force  is 
used  in  bringing  the  sections  of  the  flask  together,"  there  will, 
at  most,  be  but  a  very  thin  film  of  rubber,  nearly  impercepti- 
ble in  the  finished  work,  and  wholly  so  in  the  mouth.  To 
better  eifect  the  object  stated,  the  author  has  been  accustomed, 
when  uniting  porcelain  blocks,  to  use  a  small  magnifying  glass, 
which  reveals  inaccuracies  of  coaptation  not  apparent  to  the 
naked  eye. 

The  teeth  having  thus  been  properly  united  and  arranged, 
the  wax  rim  supporting  them  on  the  lingual  side  should  be 
cut  away  and  carved  with  heated  instruments,  especially  de- 
signed for  that  purpose,  until  the  required  form  and  fulness 
are  obtained,  adding  wax,  if  necessary,  to  the  palatal  portion 
of  the  plate,  making  it  just  enough  thicker  than  that  required 
in  the  completed  set  to  compensate  for  waste  in  the  process  of 
final  finishing.  Any  considerable  excess  of  material  should  be 
avoided,  since  it  will  not  only  materially  increase  the  labor  of 
dressing  the  vulcanized  plate,  but  tend  to  induce  sponginess  of 
the  rubber  under  heat.  A  rim  of  wax  should  also  be  extended 
around  the  front  and  lateral  borders  of  the  plate,  overlapping, 
somewhat,  the  extremities  of  the  gum  portions  of  the  teeth. 

*  Instructions  in  Vulcanite,  p.  19. 


842 


MECHANICAL   DENTISTRY. 


Wax  used  for  the  purposes  indicated  should  be  of  the  cleanest 
and  purest  varieties.  A  model  set  prepared  in  the  manner  de- 
scribed will  present  the  appearance  represented  in  Fig.  129. 

Formation  of  the  Mould  or  Matrix. — The  process  having 
been  conducted  thus  far, — any  defects  in  the  arrangement  of 
the  teeth  having  been  previously  corrected  upon  trial  of  the 
plate  in  the  mouth, — the  next  step  in  the  operation  is  the  for- 
mation of  a  mould  or  matrix  in  which  the  gum  material  is 
packed  and  pressed  preparatory  to  being  indurated  or  vulcan- 
ized. In  forming  a  matrix,  a  vulcanizing  flask  is  used,  the 
various  parts  of  which  are  separately  represented  in  Fig.  128. 


Fig.  128. 


The  lower  section  of  the  flask  A,  is  first  filled  one-half  or  two- 
thirds  full  of  plaster  mixed  with  water  to  the  consistence  of 
cream.  Into  this  the  base  of  the  model,  previously  moistened 
with  water  (the  plate  and  teeth  being  attached  to  the  model), 
is  immersed  and  additional  portions  of  the  plaster  added,  if 
necessary,  filling  the  cup  even  with  the  upper  edge,  and  ex- 
tending it  up  the  sides  of  the  model  to  the  lower  edge  of  the 
external  rim  of  wax  attached  to  the  borders  of  the  gum  plate. 
The  base  of  the  model  should  be  cut  away,  so  that  when  placed 
in  the  flask  the  lower  edge  of  the  gum  plate  will  extend  but 
little  above  the  level  of  the  upper  borders  of  the  cup.     The 


VULCANITE   BASE.  343 

surface  of  the  plaster  is  then  trimmed  smoothly,  and  coated 
with  varnish  and  then  oiled ;  all  the  exposed  portions  of  the 
gum  plate  and  wax  are  also  oiled,  leaving  the  surfaces  of  the 
teeth  untouched.  The  several  parts  will  now  present  the  ap- 
pearance represented  in  Fig.  129.  The  upper  section  of  the 
flask  J5,  is  next  placed  in  its  proper  position  over  the  lower,* — 
the  slides  formed  in  one,  and  corresponding  grooves  in  the 
other,  determining  an  accurate  relation  of  the  two  pieces. 
Into  the  upper  rim  of  the  flask,  plaster,  mixed  to  the  consist- 
ence before  mentioned,  is  now  poured,  filling  it  completely. 
The  lid  or  cap  D,  also  filled  in  with  plaster,  is  then  applied  to 

Fig.  129. 


the  opening  above,  and  the  several  parte  of  the  flask  com- 
pressed by  placing  them  within  the  clamp  C,  and  forcing  them 
together  with  the  screw,  impacting  the  plaster  and  driving  out 
the  excess  through  the  jointe  of  the  flask.  As  soon  as  conden- 
sation of  the  plaster  takes  place,  the  flask  should  be  placed  in 
a  hot-air  chamber  or  on  a  stove,  and  heated  throughout  suffi- 
ciently to  soften,  but  not  melt,  the  wax.  The  clamp  is  tlien 
removed  and  the  two  sections  of  the  flask  carefully  separated  by 
forcing  a  small  chiscl-shajjed  instrument  in  at  different  points 
between  them,  tiie  lid  closing  the  opening  above  remaining  in 
place.  On  separating  the  flask,  the  teeth,  with  the  wax  and 
temporary  plate,  will  be  found  attached  to  the  section  of  the 


344  MECHANICAL   DENTISTRY. 

matrix  last  formed,  the  portions  of  the  crowns  of  the  teeth  not 
covered  with  wax  being  imbedded  in  the  plaster  and  their 
plate  extremities  presenting  towards  the  matrix,  as  seen  in 
Fig.  130.  The  gutta-percha  plate  and  wax  should  now  be 
carefully  detached  %vith  such  instruments  as  will  best  enable 
the  operator  to  work  out  confined  portions  around  the  plati- 
num pins  and  from  the  interstices  between  the  teeth,  being 
careful  at  the  same  time  not  to  deface  the  plaster  surface  of  the 
mould.  To  relieve  the  matrix  more  perfectly  of  all  traces  of 
wax  not  accessible  to  instruments,  the  section  containing  the 
teeth  may  be  subjected  to  a  heat  sufficient  to  induce  its  com- 
plete absorption  by  the  plaster.  The  flask  should  be  heated 
gradually,  otherwise  the  contents  may  be  suddenly  and  forcibly 
ejected  in  consequence  of  the  too  rapid  evolution  of  vapor. 

Before  packing  the  material,  provision  should  be  made  for 
the  escape  of  any  excess  when  the  matrix  is  filled  and  the  two 
sections  of  the  flask  are  forced  together,  permitting  the  latter 
to  close  upon  each  other  in  exactly  the  same  manner  as  before 
the  introduction  of  the  gum.  If  the  vulcanizable  substance 
becomes  engaged  between  the  surfaces  of  the  plaster  around 
the  matrix,  the  vulcanized  base  will  be  increased  in  thickness 
just  in  proportion  to  that  of  the  interposed  layer  of  gum,  and 
hence  the  teeth  of  replacement  will  be  relatively  elongated. 
This  increased  thickness  of  the  base  and  consequent  changed 
relation  of  the  teeth  to  the  maxillary  ridge  and  to  those  of  the 
opposing  jaw,  if  but  slight,  may  be  immaterial  in  the  applica- 
tion of  full  sets  of  teeth,  but  it  is  far  different  in  the  construc- 
tion of  partial  pieces,  where  the  perfection  of  the  finished  work 
depends  in  so  great  a  degree  upon  a  faultless  preservation  of 
the  exact  position  originally  assigned  to  the  organs  of  replace- 
ment in  the  several  vacuities  on  the  ridge.  If,  for  example, 
in  replacing  the  superior  incisors,  the  approximation  of  the 
two  sections  forming  the  mould  is  obstructed  by  the  intrusion 
of  the  gum  material  between  the  plaster  surfaces,  the  teeth, 
whether  plate  or  gum,  will  be  relatively  elongated  in  propor- 
tion to  the  increased  thickness  imparted  to  the  base  consequent 
upon  the  incomplete  closure  of  the  fl.ask,  and  however  accu- 


VULCANITE   BASE. 


345 


rately  or  skilfully  the  porcelain  teeth  may  have  been  originally 
fitted  to  the  vacuity  in  front,  the  artificial  will  be  found  to 
depart  from  the  natural  gum,  while  the  porcelain  crowns  will 
be  displaced  and  projected  below  those  of  the  contiguous  natural 
organs.  Such  displacement  in  the  cases  last  referred  to,  how- 
ever small  in  degree,  cannot  fail  either  to  impair  or  destroy 
the  value,  both  as  respects  appearance  and  utility,  of  the  sub- 


stitute. The  usual  method  of  furnishing  an  exit  to  redundant 
material,  is  to  form  a  series  of  conduits  or  grooves  in  the  sur- 
face of  the  plaster  containing  the  teeth,  extending  them  from 
the  edge  of  the  matrix  to  the  rim  of  the  cup.  The  escape  of 
the  gum  will  be  facilitated  by  filing  notches  at  intervals  around 
the  rim  of  the  flask,  making  the  grooves  in  the  plaster  continu- 
ous with  them,  the  grooves  being  an  eighth  or  a  fourth  of  an 
inch  apart.  To  still  more  efFectually  j)revent  the  intrusion  of 
the  vulcanite  material  between  the  surfaces  of  the  opposing 
sections  of  plaster,  a  circular  groove  may  be  cut  in  the  plaster 


346 


MECHANICAL  DENTISTEY. 


within  a  line  or  two  of  the  margins  of  the  matrix,  into  which 
narrow  channels  at  short  distances  are  made  leading  from  the 
mould ;  others,  again,  are  made  at  wider  intervals  from  the 
circular  groove  to  the  outer  margins  of  the  flask,  terminating 
as  before  in  small  notches  formed  in  the  rim  of  the  cup. 
Fig.  130  exhibits  the  section  of  the  flask  containing  the  teeth 
with  the  channels  formed  as  described ;  the  remaining  section 
containing  the  model  is  shown  in  Fig.  131 ;  the  two  pieces 
when  closed  upon  each  other  forming  the  matrix.  Into  the 
grooved  section  of  the  mould,  the  vulcanizable  substance  is 


Fig. 131. 


packed  previous  to  being  indurated.  It  is  at  this  stage  that 
the  materials  employed  to  exclude  the  rubber  from  between 
the  teeth,  and  noticed  in  another  place,  are  packed  into  the 
joints  before  the  gum  material  is  introduced.  The  face  of  the 
model  should  also  be  coated  with  some  substance  which  will 
prevent  the  rubber  from  penetrating  the  pores  of  the  plaster, 
and  its  adhesion  to  the  surface  of  the  model.  Barker's  ethereal 
solution,  or  the  collodion  of  the  shops,  may  be  used  for  the 
purpose.  Preference  is  given  by  Professor  Wildman  to  solu- 
ble glass  or  liquid  silex,  as  being  more  readily  detached  from 
the  surface  in  finishing  than  the  preparation  mentioned.     The 


VULCANITE   BASE.  347 

latter  should  be  allowed  to  dry  perfectly  before  packing. 
Either  of  these  substances  is  best  applied  with  a  small  brush, 
coating  the  face  of  the  model  uniformly. 

Packing  the  Mould. — The  portion  of  the  flask  containing 
the  teeth  should  be  first  heated  in  an  oven  or  furnace,  or  over 
the  flame  of  a  spirit-lamp,  until  the  temperature  of  the  whole 
is  sufficient  to  render  the  vulcanizable  gum  soft  and  pliable  as 
successive  portions  are  applied  and  pressed  into  the  mould,  and 
to  retain  it  in  that  condition  until  the  operation  of  packing  is 
completed.  Narrow  strips  of  the  gum  material  should  first  be 
worked  carefully  into  the  contracted  groove  underneath  the 
platinum  pins  with  small  curved  or  straight-pointed  spear- 
shaped  steel  instruments  (Fig.  132),  adding  on  small  pieces  at 

Fig,  132, 


a  time  after  each  successive  portion  is  thoroughly  impacted, 
until  the  main  groove  of  the  matrix  over  the  base  of  the  teeth 
is  partially  filled.  The  palatal  convexity  of  the  mould  may 
then  be  covered  with  a  single  piece  cut  to  the  form  of  the  un- 
covered space  ;  a  smaller  piece  of  the  same  general  form  as  the 
latter  may  then  be  added,  giving  to  the  central  portion  a  double 
thickness  of  the  gum  plate  material,  so  that  when  the  two  sec- 
tions of  the  flask  are  brought  together,  the  excess  of  gum  in 
the  centre  will  be  forced  gradually  to  the  margins  of  the  mould, 
diminishing,  thereby,  the  liability  of  the  grooves  becoming 
prematurely  clogged  with  the  material  before  the  opposing  sec- 
tions of  the  flask  close  upon  each  other.  Especial  care  should 
be  taken  in  the  process  of  packing  to  avoid  contact  of  the  in- 
struments with  the  surface  of  the  mould,  as  fragments  of  the 
broken  plaster  are  liable  to  mix  with  the  gum  and  render  the 
surface  of  the  finished  work  imperfect  by  forming  small  pits 
wherever  such  particles  occur. 

In  regard  to  the  quantity  of  rubber  necessary  to  fill  the 
matrix  perfectly,  experience  in  its  use  will  enable  the  operator 


348 


MECHANICAL  DENTISTEY. 


to  estimate  the  capacity  of  the  mould  with  tolerable  accuracy. 
Some  small  excess  of  rubber  should  always  be  provided.  The 
required  quantity,  however,  can  be  more  certainly  determined 
by  measurement  or  weight.  A  very  simple  instrument  (Fig.  1 33), 
contrived  by  Mr.  E.  T.  Starr,  may  be  used  to  determine  the 


Fig.  133. 


quantity  by  measurement.  The  vessel  being  partly  filled  with 
water,  the  lower  point  is  adjusted  and  fixed  with  a  screw  to 
mark  its  height.  Into  this  every  particle  of  the  model  plate 
is  immersed,  and  the  rise  of  water  indicated  in  the  same  man- 
ner by  the  upper  point.  The  vessel  is  then  emptied  and  well 
cleansed,  clean  water  filled  into  the  level  of  the  lower  point, 


VULCANITE   BASE.  349 

when  rubber  is  added  in  sufficient  quantity  to  bring  the  surface 
of  the  water  on  a  level  with  the  upper  point ;  to  this  is  to  be 
added  the  necessary  excess  of  rubber  before  recommended. 

The  following  method  of  determining  the  quantity  of  rubber 
by  weight  is  given  by  Professor  Wildman : 

"  The  specific  gravity  of  wax  is  .96.  I  have  found  that  of 
the  American  Hard  Rubber  Company's  prepared  gutta-percha 
to  be  2.454,  and  the  same  company's  red  rubber  to  be  1.572. 
Hence,  to  fill  the  mould,  when  pure  wax  is  used  for  a  model 
plate,  it  will  require  to  one  part  of  wax,  by  weight,  1.6  of  the 
Company's  red  rubber ;  and  when  the  plate  is  made  of  prepared 
gutta-percha,  it  will  require  to  one  part  of  it,  by  weight,  .6  of 
red  rubber.  When  the  wax  is  colored,  the  disparity  in  weight 
will  not  be  so  great  as  with  pure  wax, 

"  Of  the  two  methods  to  ascertain  the  quantity  of  rubber, 
that  by  measure  offers  an  advantage  over  that  by  weighing,  in 
the  facility  Avith  which  it  can  be  arrived  at,  especially  when 
Starr's  instrument  is  used,  the  calculation  being  based  upon 
bulk  only ;  whilst  by  weight,  when  the  model  plate  is  composed 
of  more  than  one  substance,  as  it  frequently  is,  of  gutta-percha, 
wax,  and  sometimes  wires  introduced  to  give  stiffness,  quite 
an  intricate  calculation  must  be  made  to  ascertain  the  exact 
quantity." 

Having  completed  the  packing  of  the  mould,  the  two  por- 
tions of  the  fla.sk  are  reapplied  to  each  other  in  exactly  their 
original  relation,  being  careful  that  the  apposition  of  the  two 
is  such  that,  when  approximated,  the  guides  attached  to  one 
division  of  the  flask  shall  pass  directly  and  without  obstruction 
into  the  grooves  or  slots  in  the  one  opposite.  With  the  flasks 
first  introduced,  some  difficulty  and  uncertainty  were  often 
experienced  in  effecting  the  desired  closure  of  the  flask  on 
account  of  inherent  defects  of  construction,  but  more  recent 
improvements  have  entirely  obviated  this  difficulty.  Those 
manufactured  by  L)rs.  Hayes  and  Whitney  enjoy  deserved 
po[)ularity,  and  are,  perhaps,  in  most  general  use.  Fig.  134 
represents  one  of  Hayes's  flasks,  with  improved  clamps.  The 
lug-joint  is  so  constructed  that  the  strain  all  comes  upon  the 


350 


MECHAXICAL   DEXTISTEY. 


casting.     The  pin  only  serves  to  keep  the  lug  in  place  while 
not  in  use.     The  several  pieces  all  being  attached  together,  are 

Fig.  134. 


not  liable  to  get  lost  or  mislaid.  Whitney's  flasks,  original 
and  improved  forms,  are  shown  in  Fig.  135.  The  improve- 
ment in  construction  consists  in  reversing  the  position  of  the 


Fig.  135. 


bolts,  fitting  the  head  into  the  hole  in  the  lower  part  of  the 
flask,  and  using  a  nut  on  top. 

What  is  known  as  the  *'  Starr  Flask  "  is  highly  commended 
as  fulfilling  very  perfectly  the  requirements  of  practice.     An 


Fig.  136. 


admirable  flask,  happily  meeting  some  important  indications, 
is  represented  in  Fig.  136.     Every  operator  of  experience  is 


VULCANITE  BASE.  351 

familiar  with  the  annoyance  and  difficulty  sometimes  attend- 
ing a  satisfactory  adjustment  of  models  of  unusual  depth,  often 
of  lower  sets,  and  partial  pieces,  where  the  porcelain  teeth  are 
secured  by  the  surrounding  plaster  to  the  model — difficulties 
arising  from  the  shallowness  of  the  lower  section  of  flasks  as 
ordinarily  constructed.  The  "  Reversible  Flasks/'  invented  by 
Mr.  E.  T.  Starr,  the  different  parts  of  which  are  represented 
in  the  accompanying  cuts,  provides  very  perfectly  for  any  exi- 
gency that  may  arise  in  the  class  of  cases  mentioned.  The 
following  description  of  this  flask  is  taken  from  the  advertising 
columns  of  the  Dental  Cosmos: 

"  The  rings  of  this  flask  are  of  different  widths,  either  of 
them  fitting  the  top  or  bottom  accurately,  as  may  be  required. 

"  By  using  the  wide  ring  next  to  the  bottom,  an  admirable 
flask  is  obtained  for  deep  cases  and  partial  sets,  or  where  the 
artificial  gum  rests  on  the  natural.  The  narrov;  ring  is  used 
next  the  bottom  plate,  for  whole  dentures,  where  the  parting 
is  at  the  rim  of  the  plate.  The  bottom  has  three  countersunk 
holes,  through  which  the  plaster  runs,  and,  when  set,  holds 
the  accompanying  ring  securely  to  it.  The  fastenings  of  the 
flask  are  T-shaped  at  one  end,  and  fit  the  slots  in  the  bottom 
plate ;  and,  being  free  at  both  ends,  are  more  easily  adjusted 
than  ordinary  bolts.  The  flask  being  in  four  pieces  (two  rings 
and  two  plates),  the  plaster  is  removed  without  the  usual  trou- 
ble.    The  cuts  represent  the  flask  in  different  positions." 

The  author  has,  for  the  past  several  years,  used  exclu- 
sively, and  with  the  greatest  satisfaction,  a  flask  constructed 
with  detached  T-shaped  bolts  fitting  accurately  into  slots  or 
grooves  extending  continuously  from  top  to  bottom  of  the 
flask,  as  represented  in  Fig.  137.  The  closure  of  tlie  sections 
by  this  arrangement,  with  the  bolts  in  place,  is  unerring,  and 
is  accomplished  with  the  greatest  facility.  It  is  called  the 
'^Anchor  "  flask,  furnished  by  the  Philadelphia  Dental  Manu- 
facturing Company,  but  the  author  is  unadvised  of  the  name 
of  the  inventor. 

AVhatever  flask  is  used,  the  entire  mass  of  inclosed  rubber 
should  be  rendered  uniformly  plastic,  after  packing,  by  sub- 


352 


MECHANICAL  DENTISTRY. 


jecting  it  to  either  a  dry  heat,  such  as  may  be  obtained  with  a 
conveniently  constructed  sheet-iron  furnace,  the  baking  apart- 
ment of  an  ordinary  cooking  stove,  or  any  other  available 
means  by  which  a  diffused  and  uniform  temperature  may  be 
secured,  being  careful  not  to  overheat ;  or,  if  moist  heat  is 
employed,  by  immersing  the  flask  in  boiling  water  for  a  time 
sufficient  to  soften  the  rubber.  The  approximation  of  the  sec- 
tions of  the  flask  should  be  effected  interruptedly, — alternately 
heating  the  entire  mass  and  tightening  by  means  of  the  screw- 
bolts  until  all  the  redundant  material  is  expelled  by  degrees 


Fig.  137. 


through  the  outlets  provided  for  it,  and  the  sections  of  the 
flask  close  accurately  upon  each  other. 

A  somewhat  novel  and  ingenious  device  employed  in  pack- 
ing the  mould  is  exhibited  in  Fig.  138,  known  as  "Hayes's 
Condensing  Flask." 

To  form  the  mould,  first  smear  over  the  plunger  with  soap, 
put  into  the  flask  and  secure  it  in  place  by  a  turn  of  the  set-screw. 
Pour  in  the  plaster  and  place  the  model  in  the  usual  way, 
allowing  the  plaster  to  flow  up  and  take  the  imprint  of  the 
lower  half  of  the  plunger.  When  the  teeth  are  in  place  the 
back  edge  of  the  plate  must  be  connected  with  the  plunger  by 
a  broad  strip  of  wax  reaching  across  its  entire  face,  to  form  a 
gateway,  or,  if  an  under  set,  two  strips  connecting  the  plunger 


VrLCANITE   BASE. 


353 


with  the  mould  on  each  side  opposite  the  molar  teeth.  These 
strips  may  be  thickened  a  little  where  they  connect  with  the 
plunger,  to  allow  a  free  flow  of  rubber  into  the  mould.  Also 
lay  a  narrow  strip  of  wax  from  the  mould  to  the  notch  in  the 
front  edge  of  the  flask,  from  which  the  rubber  will  protrude 
and  show  when  the  mould  is  full.  Then  put  on  the  upper 
section,  fill  with  plaster,  and  drive  on  the  cover  before  the 
plaster  sets. 

AVhen  hard,  first  withdraw  the  plunger,  then  open  the  flask 
and  remove  the  wax  in  the  usual  way.  Take  once  and  a  half 
as  much  rubber  by  measure,  or  three  times  as  much  by  weight, 
as  there  was  of  the  wax.     There  is  no  occasion  to  warm  either 


Fig.  138. 


the  mould  or  the  rubber.  Cut  into  strips,  lay  as  much  into  the 
mould  as  may  be  without  preventing  the  flask  from  closing,  and 
place  the  balance  within  the  cavity  formed  by  the  plunger. 
Now  close  tlie  flask,  again  smear  the  plunger  with  soap  and 
press  it  into  the  flask  as  far  as  it  will  go.  Then  connect  the 
flask  with  the  screw- press,  turn  down  the  set-screw  firmly 
upon  the  flask,  and  place  the  whole  in  the  open  vulcanizer  two- 
thirds  filled  with  water.  When  it  boils  freely,  turn  down  the 
screw — not  faster  than  one  revolution  a  minute — till  rubber 
appears  at  the  opening  in  front  left  for  that  purpose. 

Sliould  there  be  a  surplus  of  rubber,  it  may  be  withdrawn 
with  the  plunger,  by  leaving  the  end  without  soap;  or  it  may 
be  left  in  and  removed  with  the  plaster  after  the  piece  is  vul- 
canized. In  either  ca.se  there  is  no  need  of  closing  the  cylin- 
der while  vulcanizing,  as  the  rubber  in  the  mould  will  not  be 

23 


354  MECHANICAL  DENTISTRY. 

displaced.  If  desired,  however,  the  cylinder  may  be  filled 
with  plaster  or  a  cork.  Should  the  plunger  be  used  without 
soap,  the  rubber  will  adhere  somewhat,  but  will  do  no  harm, 
as  it  is  easily  removed  by  a  cloth  moistened  with  kerosene  or 
naphtha.  In  driving  on  the  cover,  or  removing  it  from  the 
flask,  a  few  light  blows  with  a  small  mallet  serves  the  purpose 
best,  and  will  not  batter  the  metal. 

The  packing  accomplished,  the  piece  is  ready  for  the  vulcan- 
izing process. 

Vulcanizing. — The  process  of  vulcanizing  or  hardening  the 
various  rubber  compounds  employed  for  dental  purposes  is 
eifected  by  subjecting  them  for  variable  periods  of  time  to  the 
action  of  heat,  the  substances  to  be  acted  on  being  confined 
within  a  steam-chamber  constructed  for  the  purpose.     The 

Fig.  139. 


time  and  temperature  necessary  to  produce  the  requisite  in- 
duration differ  with  the  various  compounds  in  use,  and,  to 
some  extent,  are  influenced  by  the  kind  of  vulcanizing  ap- 
paratuses employed  and  which  present  various  modifications  of 
form  and  mechanism,  being  constructed,  in  part,  with  refer- 
ence to  the  source  and  mode  of  application  of  the  heat,  the 
former  being  derived  either  from  coal  or  charcoal,  or  other 
solid  combustible  substances,  or  from  the  flame  of  a  spirit- 
lamp,  gas,  or  coal  oil  or  some  of  its  products. 

As  fuel  is  no  longer  employed  in  vulcanizing,  any  descrip- 
tion of  the  apparatuses  specially  adapted  to  this  mode  of  pro- 
ducing heat  is  deemed  unnecessary.     They  have  been  entirely 


VULCANITE  BASE. 


355 


superseded  by  others  of  improved  form  and  construction  adapted 
to  the  use  of  either  gas,  alcohol,  or  coal  oil  and  its  products, 
for  heating  purposes.  Fig.  139  represents  one  of  Dr.  Hayes's 
Single  Flask  Iron-clad  Ovens,  convenient  and  compact  in 
form,  and  capable,  it  is  claimed,  of  vulcanizing  in  40  minutes 
at  a  temperature  of  320°,  with  one  ounce  of  alcohol.  Instru- 
ments of  similar  construction  are  produced  by  the  same  manu- 


Fm.  140. 


Fig.  141. 


facturer  with  a  larger  boiler  capacity  for  from  one  to  three 
cases.  Figs.  140,  141. 

The  iron-clad  improvement  in  these  machines  is  designed 
as  a  protection  from  the  dangers  of  explosion  consequent  upon 
a  gradual  thinning  of  the  copper  boiler  from  corrosion,  a  safe- 
guard of  great  practical  value  and  concern  to  those  who  are 
continually  exposed  to  the  perils  of  such  an  accident.  The 
shell  is  made  of  malleable  iron,  J  inch  thick — strong  enough 
to  resist  many  times  the  strain  required  ;  and  can  never  be 
exposed  to  deterioration.  The  copper  lining  is  made  the  same 
thickness  as  the  copper  boilers  now  in  use,  and  the  machine 
may  be  used  with  perfect  safety,  even  when  the  copper  has 
become  as  thin  as  paper,  and  then,  when  an  opening  has  been 
fairly  cat  through,  steam  will  escape  from  between  it  and  the 


356 


MECHANICAL   DENTISTRY. 


iron  shell,  below  the  packing  joint,  giving  timely  notice  that 
a  new  lining  is  required,  which  can  be  inserted  at  moderate 
expense,  and  render  the  vessel  good  and  safe  as  new. 

A  peculiar  and  important  feature  of  these  vulcanizers  is  in 
placing  the  thermometer  bulb  within  a  mercury  bath,  outside 
the  steam-chamber,  relieving  it  entirely  from  the  danger  of 
being  crushed  or  checked  by  the  pressure  of  steam,  as  is  liable 


Fig.  142. 


t^^tv/' 


to  happen  when  it  is  exposed  to  the  steam  itself,  necessitating 
its  frequent  replacement. 

A  not  less  convenient,  safe,  and  reliable  vulcanizer  is  that 
known  as  Dr.  Whitney's,  represented  in  Fig.  142,  having  a 
steam-chamber  capacity  for  from  one  to  three  flasks.  The 
boiler  is  made  of  wrought  copper ;  the  top  or  cap,  which  is 
screwed  on,  being  provided  with  a  thermometer,  and  an  aper- 
ture filled  with  fusible  metal,  which  renders  explosion  of  the 
boiler,  unless  materially  weakened  by  corrosion,  impossible. 
The  author  has  had  one  in  constant  use  for  many  years  with- 
out any  perceptible  deterioration. 

A  well-approved  instrument,  called  the  "  Buckeye  Vulcan- 
izer," invented  by  Dr.  C.  H.  James,  of  Cincinnati,  Ohio,  is 


VULCANITE   BASE. 


357 


exhibited  in  Fig.  143.  The  mechanism  of  this  instrument  is 
remarkably  simple  and  ingenious,  the  relation  of  the  diiferent 
parts  being  plainly  exhibited  in  the  accompanying  cuts.  The 
top  is  very  quickly  and  readily  adjusted,  and  is  clamped  and 
held  securely  in  place,  making  a  steam-tight  joint,  by  a  single 
set-screw  acting  upon  the  centre  of  the  cover. 

The  application  of  heat  derived  from  coal  oil  and  its  prod- 
ucts, for  the  purpose  of  vulcanizing,  is  shown  by  the  accom- 


FlG.  143. 


panying  cut  (Fig.  144),  which  represents  what  is  advertised 
a.s  "JIuWn  Petroleum  Gas  Burner/^  and  which  the  inventor 
claims  is  "a  lamp  by  which  coal  oil  and  its  products  can  be 
substituted  for  gas  or  alcohol  for  heating  purposes.  This  ap- 
paratus will  burn  Benzine  with  perfect  safety,  and  with 
greater  heat  than  either  gas  or  alcohol,  and  free  from  smoke. 
The  cut  will  show  its  adaptation  for  vulcanizing,  and  can  be 


358 


MECHANICAL  DENTISTRY. 


used  for  any  other  purpose.     There  is  an  attachment  for  a 
compound  blowpipe." 


Whatever  form  of  vulcanizing  apparatus  is  used,  or  means 
of  heating  adopted,  the  flasks  are  introduced  and  sufficient 
water  poured  in  to  cover  them.  If  the  flasks  are  hot  when 
placed  in  the  boiler,  water  of  nearly  the  same  temperature 
should  be  added  to  avoid  fracturing  the  teeth.  Before  screw- 
ing on  the  cap,  the  rubber  packing  should  be  dusted  with 
whiting  or  pulverized  soapstone  to  prevent  adhesion.  As  it  is 
very  important  to  secure  a  steam-tight  joint,  the  packing  should 
be  of  uniform  thickness,  firm,  and  securely  fixed.  The  webbed 
rubber  is  the  best  for  the  purpose.  In  arranging  a  new  pack- 
ing, cleanse  w^ell  the  groove  in  the  boiler  which  receives  the 
rim  of  the  cap,  and  fit  the  packing  accurately.  Before  screw- 
ing on  the  top,  dust  the  surface  of  the  packing  as  before  recom- 
mended, and  as  the  heat  rises  tighten  the  screw  from  time  to 
time  until  the  rubber  no  longer  yields.     If  the  latter  precau- 


VULCANITE   BASE.  359 

tion  is  not  observed,  the  packing  is  either  liable  to  blow  out  or 
the  joint  leak  steam.  To  insure  uniform  results  it  is  necessary 
that  there  should  be  absolutely  no  leakage. 

When  the  flasks  are  properly  secured  within  the  steam- 
chamber,  heat  is  applied  and  continued  until  the  requisite  in- 
duration of  the  gum  is  effected.  The  time  and  degrees  of  heat 
necessary  to  effect  this  result  differ  somewhat  with  the  rubber 
compounds  and  kind  of  vulcanizer  employed.  The  heat  should 
be  raised  gradually  until  the  thermometer  indicates  the  proper 
vulcanizing  temperature,  when  the  flame  should  be  lowered,  aud 
the  heat  maintained  at  this  point  until  vulcanization  is  com- 
pleted. In  all  cases  it  is  best  to  raise  the  heat  slowly  until  it 
reaches  320°,  which  temperature  should  not  be  attained  in  less 
than  from  one-half  to  three-quarters  of  an  hour.  Where  there 
is  any  considerable  or  unusual  body  of  rubber,  the  time  taken 
to  raise  the  heat  to  that  point  should  be  extended  to  one  hour 
or  longer,  for  if  the  mass  is  heated  too  rapidly,  porosity  or 
sponginess  of  the  thicker  portions  of  the  rubber  will  almost 
certainly  ensue.  This  result  would  seem  to  be  due  to  the  en- 
ergetic evolution  of  sulphuretted  hydrogen  gas  under  a  quick 
heat,  the  proper  elimination  of  which  is  checked  and  the  gas 
confined  within  the  body  of  the  mass  by  a  too  rapid  surface 
induration  of  the  rubber.  The  evolution  of  this  gas  is  demon- 
strated by  Professor  Wildman  in  the  following  experiment : 

"  To  ascertain  if  sulphuretted  hydrogen  is  given  off  during 
vulcanization,  a  bulb  was  blown  at  the  end  of  a  glass  tube; 
this  was  filled  with  red  rubber;  the  tube  was  then  drawn  out 
very  small  from  immediately  above  the  bulb,  and  curved  so 
that  the  small  part  when  the  bulb  was  in  the  paraffin  bath 
could  be  inserted  into  a  vessel  beside  it. 

"The  bulb  was  then  placed  in  a  paraffin  bath,  and  the  curved 
end  of  the  tube  inserted  in  a  vessel  containin";  a  solution  of 
acetate  of  lead.  The  heat  was  raised  to  320°  F.,  and  retained 
at  that  point  for  one  hour  and  a  quarter. 

"The  mean  result  of  several  experiments  conducted  in  this 
manner  was,  that  during  the  first  thirty  or  forty  minutes  after 
the  heat  had  attained  to  320°,  bul)bles  of  sulphuretted  hydro- 
gen came   over   at  short  intervals,  and  at  the  expiration  of 


360  MECHANICAL   DENTISTEY. 

this  time  it  was  evolved  in  a  continuous  stream,  which  con- 
tinued for  a  few  minutes,  causing  a  copious  precipitate  of  sul- 
phide of  lead.  After  this,  until  the  expiration  of  the  hour  and 
a  quarter,  the  gas  was  only  given  ofiP  sparingly  at  intervals. 
This  experiment  gives  us  ocular  demonstration  that  this  gas 
is  evolved  during  vulcanization,  and  in  large  quantities,  and 
conclusively  shows  that  in  thick  pieces,  especially,  the  heat 
should  be  slowly  raised,  and  the  rubber  should  be  under  strong 
pressure  to  insure  a  successful  result." 

When  the  American  Hard  Rubber  Company's  red  rubber 
is  used,  the  heat  should  be  maintained  at  320°  for  about  one 
hour  and  ten  or  twenty  minutes.  Induration  may  be  effected 
at  a  lower  heat,  but  the  time  must  be  proportionally  extended  ; 
or  a  higher  heat  being  employed,  a  less  time  will  be  required 
to  vulcanize.  With  the  use  of  the  rubber  mentioned,  the 
author  has  obtained  good  results  by  vulcanizing  for  45  min- 
utes at  340°.  Care,  however,  should  be  taken  not  to  over- 
heat, as  the  rubber  is  thereby  rendered  dark  and  brittle,  and 
the  important  property  of  elasticity  impaired.  The  time  and 
degrees  of  heat  first  mentioned,  therefore,  may  be  regarded  as 
the  safest,  and  as  yielding  the  best  results,  though  with  other 
rubber  compounds,  and  the  use  of  modified  forms  of  vulcanizers, 
corresponding  differences  in  time  and  temperature  may  be  re- 
quired, and  which  can  only  be  accurately  determined  by  vul- 
canizing test-pieces  of  rubber. 

In  this  connection  the  reader's  attention  is  called  to  some 
practical  observations  on  the  subject  of  steam  pressure  in  vul- 
canizing, and  the  reliability  of  thermometers  as  indicators  of 
heat,  and  which  acquire  additional  interest  if  it  be  true,  as 
alleged,  that  many  of  the  vulcanizers  in  use  by  dentists  are 
insecure,  by  reason  of  inherent  defects  of  construction,  or 
faultiness  in  the  modes  of  indicating  the  elastic  force  of  steam. 
In  commenting  on  this  subject.  Professor  Wildman  observes  :* 

"  As  high  steam  is  used  in  vulcanizing,  it  is  important  that 

the  operator  should  be  conversant  with  the  nature  of  the  agent 

which  he  employs  to  accomplish  his  end.     It  is  perfectly  safe ; 

but  the  following  will  show  him  that  it  must  be  used  with 

*  Instructions  in  Vulcanite,  p.  26. 


VULCAXITE    BASE.  3G1 

discretion  and  judgment.  Numerous  experiments  have  been 
made  bv  scientific  men  to  ascertain  the  elastic  force  of  steam 
at  diflerent  temperatures.  The  results  of  their  investigations 
are  not  uniform ;  although  they  all  agree  in  showing  the  im- 
mense force  exerted  by  this  agent  at  high  temperatures.  Has- 
well's  tables  are  looked  upon  as  good  authority.  The  results 
of  the  investigations  of  the  Franklin  Institute  Committee,  in 
the  higher  degrees,  give  a  greater  elastic  force  than  the  table 
below  quoted.  I  shall,  however,  quote  the  results  of  the  ex- 
periments of  the  commission  of  the  French  Academy,  appointed 
by  the  French  government  to  investigate  this  subject,  for  the 
reasons  that,  from  the  manner  in  which  they  were  conducted, 
they  are  probably  as  reliable  as  any,  and  that  they  are  extended 
to  a  more  elevated  temperature  than  the  others. 


Elasticity  of  steam, 
taking  atmospheric 
pressure  as  unity. 
1 

Temperature  F. 
212° 

Pressure  per  square 
inch,  pounds. 
14.7 

u 

233.96° 

22.05 

2 

250.52° 

29.4 

2h 

263.84° 

36.75 

3 

275.18° 

44.1 

3} 

285.08° 

51.45 

4 

293.72° 

58.8 

4} 

300.28° 

66.15 

5 

307.05° 

73.5 

ol- 

314.24° 

80.85 

6 

320.36° 

88.2 

6} 

326.26° 

95.55 

7 

331.70° 

102.9 

7h 

336.86° 

110.85 

8 

341.78° 

117.6 

9 

350.78° 

132.3 

10 

358.88° 

147 

11 

366.85° 

161.7 

12 

374.00° 

176.4 

13 

380.00° 

191.1 

14 

386.94° 

205.8 

15 

392.86° 

220.5 

16 

398.48° 

235.2 

17 

403.82° 

249.9, 

18 

408.92° 

264.6 

19 

413.78° 

279.3 

20 

418.40° 

294 

362  MECHANICAL   DENTISTRY. 

"  I  would  here  call  the  attention  of  those  using  high  steam 
to  an  important  consideration.  In  raising  steam,  the  ratio  of 
increase  of  pressure  or  elastic  force  is  far  greater  than  that  of 
the  increase  of  temperature. 

"By  referring  to  the  above  table,  commencing  at  212°  and 
taking  steps  as  near  fifty  degrees  as  is  given  in  the  ascending 
scale,  we  find  this  exemplified.     Thus : 

Increase  of  tempera-  Increase  of  force  per         Giving  a  force  per 

ture.  square  inch.  square  inch. 

From  212°     to  263.84°  =  51.85°  22.05  lbs.  36.75  lbs. 

"      336.84  to  314.24°  =  50.40°  44.10  lbs.  80.85  lbs. 

"      314.24  to  366.85°  =  52.61°  80.85  lbs.  161.85  lbs. 

"      366.85  to  418.46°  =  51.61°  132.15  lbs.  294  lbs. 

"  This  comparison  shows  clearly  how  rapidly  the  pressure 
increases  at  high  temperatures,  and  warns  the  operator  that 
a  strong  instrument,  combined  with  care  and  judgment  in  its 
treatment,  are  indispensable  to  safety.  Besides  the  rapid  in- 
crease of  pressure,  it  must  be  borne  in  mind  that  at  high  tem- 
peratures, copper,  of  which  the  boiler  is  composed,  becomes 
weakened,  and  in  a  measure  loses  its  power  to  resist  this  great 
imprisoned  force.  Copper,  in  passing  from  212°  to  230°  F., 
loses  about  one-tenth  of  its  strength,  and  at  550°  it  has  lost 
one-fourth  of  its  tenacity." 

In  a  paper  read  before  the  Massachusetts  Dental  Associa- 
tion, January,  1865,  Dr.  A.  Lawrence  affirms  that  "most 
vulcanizers  are  now  made  of  sheet  copper  one-sixteenth  of  an 
inch  in  thickness,  and,  agreeably  to  the  foregoing  facts,  have  a 
tensile  strength  of  1875  pounds;  and  one  four  inches  in  diame- 
ter will  not  sustain  a  pressure  of  more  than  150  pounds  per 
square  inch,  or  a  temperature  of  363°. 

"  Let  us  next  ascertain  what  force  of  steam  is  exerted  upon 
the  boiler  within  a  short  range  of  temperatures.  We  find  by 
the  tables  of  Haswell,  King,  and  others,  that  at  320°  the  pres- 
sure is  85  pounds;  at  324°,  90  pounds;  at  328°,  95  pounds; 
and  at  332°,  it  is  100  pounds  per  square  inch.  These  figures  I 
have  verified  by  a  steam  gauge  connected  with  my  own  vulcan- 
izer,  and  which  I  now  use  in  preference  to  the  thermometer,  as 
I  consider  it  more  convenient,  safer,  and  less  liable  to  accidents. 


VULCANITE   BASE.  363 

"  Practical  engineers  concur  in  the  opinion  that  a  force  of 
not  over  one-half  the  sustaining  capacity  of  the  boiler  can  be 
safely  applied." 

The  logical  deduction  from  these  statements  is  plain.  If  a 
boiler  four  inches  in  diameter,  constructed  of  sheet  copper  one- 
sixteenth  of  an  inch  thick,  will  not  sustain  a  pressure  of  more 
than  1 50  pounds  per  square  inch,  and,  accepting  as  true  what 
is  affirmed  by  practical  engineers,  "  that  a  force  of  not  over  one- 
half  the  sustaining  capacity  of  the  boiler  can  be  safely  applied," 
then  every  operator  who,  with  the  use  of  such  an  instrument, 
vulcanizes  at  a  heat  of  320°  is  in  hourly  jeopardy  of  life  and 
limb. 

Intimately  connected  with  the  process  of  vulcanizing  is  the 
question  of  the  reliability  of  thermometers  as  indicators  of 
heat,  or  steam-pressure.  Dr.  Lawrence,  commenting  on  this 
subject,  says:  "Suppose  the  bulb  of  the  thermometer  gets 
slightly  fractured,  and,  the  accident  not  being  discovered,  the 
vulcanizer  is  put  to  use,  what  then? 

"  If  the  damage  is  slight,  the  mercury  may  still  be  made  to 
rise  in  the  tube  at  high  temperatures,  but  will  not  truly  indi- 
cate the  full  heat  or  force  within.  Some  time  ago,  I  had  some 
difficulty  in  producing  a  desirable  shade  in  my  vulcanite 
work ;  it  was  too  dark,  as  is  the  case  when  overheated,  and 
I  came  to  the  conclusion  that  the  gum  had  deteriorated  in 
quality.  Other  samples  of  gum  were  tried,  and  at  varying 
lengths  of  time,  yet  with  the  same  result. 

"  No  defect  could  be  discovered  in  the  thermometer  by  the 
naked  eye,  but  a  microscope  revealed  a  slight  crack  in  the 
bull),  and  the  mystery  was  solval.  But  what  force  of  steam 
was  produced  during  these  almost  despondent  trials? 

"Although  my  vulcanizer  would  safely  bear  a  pressure  of 
one  hundred  pounds  per  square  inch,  I  concluded  to  use  a 
steam  gauge  for  the  future,  and  now  feel  a  security  in  its  use 
positi  vely  refresh i ng." 

Tlie  unreliability  of  thermometers,  in  connection  with  vul- 
canizers,  has  been  recognized  by  many  in  the  profession  who 
liave  testified  to  their  uncertainty  and  insecurity  as  a  means  of 


364  MECHANICAL   DENTISTRY. 

determinins:  with  exactness  at  all  times  the  amount  of  steam- 
pressure  employed  in  the  process  of  vulcanizing  at  a  high  heat. 
The  steam  gauge  (Fig.  145),  spoken  of  by  Dr.  L.,  seems  very 
perfectly  to  fulfil  the  requirements  of  the  dentist,  and  may 
justly  claim  favorable  consideration  from  the  commendation 
bestowed  upon  it  by  tlie  distinguished  gentleman  who  has 
brought  it  to  the  notice  of  the  profession.  The  following  is 
the  author's  own  account  of  the  instrument :  "  The  gauge  most 
suitable  for  the  purpose  in  question,  somewhat  resembles  a 
small  circular  clock ;  is  about  six  inches  in  diameter  and 
marked  to  register  one  hundred  and  forty  or  one  hundred  and 
eighty  pounds  pressure,  with  pound  dots  near  the  outer  circle 
of  the  dial.     A  pointer  indicates  the  force  which  moves  it. 

"  This  size  is  better  than  a  smaller  one,  because  the  spring 
inside  not  being  crowded  to  its  utmost  capacity  in  vulcanizing, 
will,  of  course,  retain  its  working  integrity  longer ;  in  fact,  as 
long  as  any  dentist  now  living  will  be  personally  interested  in 
the  matter.  The  price  of  such  a  gauge,  at  this  time,  is  |18  ; 
and,  though  more  expensive  ones  can  unquestionably  be  made, 
they  are  no  more  reliable,  the  difference  consisting  in  mere 
'  outward  show  and  adorning.'  They  can  be  used  with  all 
vulcanizers  generating  steam,  connecting  by  means  of  three  or 
four  feet,  or  as  much  more  as  may  be  convenient,  of  small  pipe 
having  a  U-shaped  bend,  or  a  single  coil  near  and  under  the 
gauge  to  receive  the  condensed  steam,  as  water  alone  should 
enter  that  instrument. 

"  The  following  table  exhibits  a  range  of  pressure  sufficient 
for  vulcanizing  purposes,  with  the  temperature  necessary  to 
produce  the  same. 


Pressure 

Tempera- 

Pressure 

Tempera- 

Pressure Tempcra- 

Pressure 

Tempera- 

in lbs. 

ture. 

in  lbs. 

ture. 

in  lbs. 

ture. 

in  lbs. 

ture. 

60 

295° 

69 

305° 

78 

314° 

95 

328° 

61 

296° 

70 

306° 

79 

314° 

100 

332° 

62 

298° 

71 

307° 

80 

315° 

105 

335° 

63 

299° 

72 

308° 

81 

316° 

110 

339° 

64 

300° 

73 

309° 

82 

317° 

115 

342° 

65 

301° 

74 

310° 

83 

318° 

120 

345° 

66 

302° 

75 

311° 

84 

319° 

125 

349° 

67 

303° 

76 

312° 

85 

320° 

130 

352° 

68 

304° 

77 

313° 

90 

324° 

VULCANITE   BASE. 


365 


"  It  will  readily  be  seen  by  the  above,  that  a  pressure  of 
sixty  pounds  requires  a  temperature  of  two  hundred  and  ninety- 
five  degrees  by  Fahrenheit's  scale  to  produce  it,  and  eighty- 
five  pounds  three  hundred  and  twenty  degrees,  at  which  latter 
pressure  I  vulcanize,  running  one  hour,  and  with  the  most 
satisfactory  results. 

"  The  manner  of  putting  up  and  using  the  gauge  is  very 
simple.  All  that  is  required  is  to  secure  it,  by  screws  passing 
through  the  flange  on  the  back,  in  some  conspicuous  and  con- 
venient place,  attach  a  pipe  and  carry  it  down  ten  or  twelve 
inches,  give  it  a  bend  or  curve  upward  about  half  its  length, 
or  five  or  six  inches,  thence  at  right  angles  or  otherwise,  and 
in  any  convenient  length  not  less  than  three  feet,  to  the  vul- 
canizer. 

"  The  annexed  cut  is  from  a  photograph  of  a  Whitney  vul- 
canizer  with  the  gauge  attached,  but  is  by  no  means  the  only 


Fig.  145. 


arrangement  which  can  be  made,  as,  in  some  cases,  convenience 
may  require  more  pipe,  or  a  different  distribution. 

"A,  table  or  work-bench;  B,  vulcanizer;  C,  side  outlet 
pendant  cock  screwed  on  in  [)lace  of  the  thermometer  scale ; 
D,  cou[)ling  joint;  K,  angle  in  the  pipe;  F,  iron  pipe,  three- 
sixtcentlis  in.side;  G,  U-shaj)ed  curve,  five  or  six  inches  in 
depth  ;  J  I,  cock  to  the  gauge  ;  I,  gauge. 


366  MECHANICAL  DENTISTEY. 

"  The  fitting,  putting  up  and  arranging  the  entire  apparatus 
can  be  done  in  an  hour's  time  by  any  gasfitter,  or^  to  those 
residing  away  from  cities  or  towns  where  such  mechanics  are 
employed,  can  be  furnished  to  order  by  them,  or  by  the  parties 
furnishing  the  gauge. 

"  All  the  joints,  from  the  vulcanizer  to  the  gauge,  except 
the  coupling,  should  be  '  leaded '  with  very  thick  lead  paint, 
and  screw  together  steam  tig-ht. 

"  In  using  the  apparatus,  the  cocks  C  and  H  must  be  turned 
straight  with  the  pipe,  for  if  shut  oif  at  either  point,  the  gauge 
cannot  be  acted  upon  by  the  steam.  I  generally  heat  the  water 
in  the  vulcanizer  nearly  or  quite  to  the  boiling-point,  and  let 
oif  the  heated  air  by  turning,  or  allowing  to  remain  open,  the 
cock  C,  then  connect  at  the  coupling  D,  turning  the  nut  tight 
(not  too  tight)  with  a  wrench. 

"  So  soon  as  steam  begins  to  form,  it  is  condensed  by  con- 
tact with  the  cold  part  of  the  pipe,  and  falls  into  and  fills  the 
curve  or  coil  with  water,  which  is  then  forced  into  the  gauge 
with  a  power  indicated  by  the  pointer«on  the  dial.  The  pipe 
should  descend  a  trifle  from  the  angle  E  to  the  commencement 
of  the  curve,  to  facilitate  the  passage  of  the  condensed  steam  to 
that  point. 

"  Although  vulcanizing  one  hour  at  eighty-five  pounds  af- 
fords results  satisfactory  to  me,  others  may  prefer  a  diiferent 
time  with  more  or  less  heat. 

"  The  table  will  be  found  a  guide  in  such  cases. 

"  When  the  time  is  up,  discontinue  the  fire,  and  shut  oif 
the  steam  by  turning  the  cock  C.  Turn  the  cock  H  in  the 
same  manner,  to  prevent  a  too  sudden  reverse  movement  of 
the  machinery  of  the  gauge,  the  pressure  on  which  should  be 
gradually  relieved  at  any  convenient  time. 

"  Now  disconnect  by  unscrewing  the  coupling  and  dispose 
of  the  steam  in  the  vulcanizer  by  blowing  oif,  or  any  other 
means  preferred.  Further  remarks  would  seem  unnecessary 
to  a  full  understanding  of  the  subject.  Having  used  the  gaiige 
almost  every  day  for  about  six  months,  I  am  fully  satisfied 
that  it  is  a  decided  improvement  in  vulcanizing,  and  am  so  de- 


VULCANITE   BASE. 


367 


liglited  with  it  that  no  reasonable  sum  would  induce  me  to 
substitute  the  thermometer." 

AVhen  the  process  of  vulcanizing  has  been  conducted  a  suffi- 
cient length  of  time,  the  flame  is  turned  oif  and  the  steam  dis- 
charged through  the  safety-valve,  if  the  vulcanizer  is  provided 
with  one ;  or  the  lower  half  of  the  boiler  may  be  placed  in 
cold  water  until  the  contents  are  cooled  down  to  about  200°. 
When  time  will  permit,  however,  it  is  better  to  let  the  vul- 
canizer cool  gradually.  The  top  is  then  taken  off  and  the 
flasks  removed.  The  latter  should  always  be  allowed  to  cool 
gradually,  as  the  immersion  of  the  flask,  while  hot,  in  cold 
water  will  endanger  the  porcelain  teeth  by  a  too  sudden  change 
of  temperature.  Neither  should  the  flask  be  opened  while  hot, 
for  the  plate  being  pliable  when  heated,  would  be  liable  to  suf- 
fer some  change  of  form  in  forcing;  the  sections  of  the  flask 
apart,  or  in  removing  the  piece  after  separation  of  the  flask. 
When  the  plate  is  removed  from  the  flask,  detach  carefully  all 
adhering  plaster  with  a  pointed  knife,  and  cleanse  well  by 
washing  with  a  stiff  brueh. 

Finishing. — The  rougher  and  more  redundant  portions  of 
the  indurated  material  are  first  removed  with  coarse  files  or 

Fig.  146. 


rasps,  following  with  those  of  a  finer  cut  until  all  parts  of  the 
piece  accessible  to  such  instruments  arc  reduced  to  nearly  the 
thickness  required.  The  excess  of  material  on  tiie  lingual  side 
of  the  plate  and  other  points  not  admitting  of  the  use  of  the 


368  MECHANICAL  'dENTISTEY. 

file,  is  removed  with  scrapers  of  various  forms,  some  of  which 
are  shown  in  Fig.  146.  After  nearly  the  desired  thickness  is 
thus  obtained,  and  the  surface  rendered  somewhat  smooth  and 
uniform,  a  still  further  reduction  is  obtained  with  the  use  of 
sandpaper,  using  first  the  coarser  and  finishing  with  the  finer 
kinds.  The  final  polish  is  then  given  to  the  surface,  first  with 
the  use  of  finely  pulverized  pumicestone,  and  afterwards  with 
either  prepared  chalk  or  whiting.  The  best  method  of  apply- 
ing the  pumice  is  with  flat  circular  pieces  of  cork  of  various 
sizes,  which  may  be  readily  formed  by  attaching  them  to  the 
lathe  and  reducing  them  to  the  proper  size  and  shape  with  a  file 
while  revolving.  The  chalk  or  whiting  may  be  applied  upon  a 
cotton  or  ordinary  brush  wheel.  In  the  use  of  the  polishing 
materials,  the  latter  should  be  kept  constantly  and  freely  satu- 
rated with  cold  water  throughout  the  operation. 

Partial  Dentures  Constructed  in  a  Base  of  Rubber. — The 
foregoing  description  of  the  method  of  forming  entire  dentures 
in  a  base  of  indurated  gums,  together  with  a  knowledge  of  the 
manner  of  constructing  parts  of  sets- of  teeth  mounted  on 
metallic  plates,  will  render  any  extended  description  of  the 
former  process,  as  it  relates  to  partial  pieces,  unnecessary.  A 
gutta-percha  plate  of  the  required  thickness  and  dimensions  is 
accurately  moulded  to  a  model  of  the  parts,  the  narrower  por- 
tions passing  into  the  spaces  between  the  teeth  being  stiffened 
by  doubling  the  plate  at  these  points  with  an  additional  strip 
of  gutta-percha  warmed  at  the  lamp  and  made  to  adhere  to 
the  primary  plate.  The  central  portion  of  the  plate  may  also 
be  temporarily  supported,  and  its  form  preserved,  by  filling  in 
the  concavity  with  a  layer  of  stiffened  wax.  A  rim  of  wax  is 
then  attached  in  the  usual  manner  to  those  portions  of  the  plate 
occupying  the  vacuities  on  the  ridge,  when  the  plate  is  placed 
in  the  mouth  and  an  impression  of  the  points  of  the  opposing 
teeth  secured  ;  it  is  then  removed,  reapplied  to  the  model  and 
the  heel  of  the  latter  extended  posteriorly  to  form  an  articu- 
lating surface  for  the  remaining  portion  of  the  antagonizing 
model, — the  latter  being  formed  in  the  ordinary  way.  The 
teeth  are  then  fitted  to  the  vacuities  in  precisely  the  same  man- 


VULCANITE   BASE.  369 

ner  as  when  metallic  plates  are  used,  and  the  wax  trimmed  to 
the  required  fulness.  The  plate,  with  the  teeth  attached,  is 
then  placed  in  the  mouth  and  any  necessary  corrections  made 
in  the  arrangement  of  the  teeth  ;  after  which  it  is  removed  and 
readjusted. 

In  constructing  partial  sets  of  vulcanite,  it  is  of  the  first  im- 
portance, when  forming  the  mould,  that  the  relation  of  the 
porcelain  teeth  to  the  model  of  the  mouth  should  be  accurately 
maintained,  the  reasons  for  which  are  fully  set  forth  when 
treating  of  the  formation  of  the  mould  or  matrix  for  full  sets. 
To  secure  this  result  with  certainty  the  following  method 
should  be  adopted.  Having  adjusted  the  plate  and  teeth  upon 
the  model,  with  the  wax  trimmed  and  carved  to  the  required 
fulness,  place  the  model  in  the  lower  section  of  the  flask  and 
fill  in  with  plaster,  extending  it  up  to  the  points  of  the  teeth, 
binding  them  to  the  model,  and  making  the  line  of  separation 
of  the  sections  of  the  flask  at  that  point.  The  ends  of  the 
plaster  teeth  should  be  cut  away  sufficiently  to  allow  of  a  ready 
separation  of  the  sections.  Plaster  is  then  poured  in  for  the 
upper  section  of  the  mould,  and,  when  hard,  the  flask  is  parted 
and  the  wax  removed  from  the  model  and  teeth,  the  latter 
being  retained  in  the  lower  instead  of  the  upper  section  as  in 
full  cases. 

Metallic  Clasps  attached  to  Rubber  Plates. — Although  at- 
mospheric pressure  should  be  made  available  in  all  practicable 
cases  as  a  means  of  retaining  parts  of  sets  of  teeth  in  the  mouth, 
yet  cases  occasionally  present  themselves  necessitating  the 
employment  of  clasps.  These  may  be  of  rubber,  but  those 
formed  of  gold,  or  gold  alloyed  with  platina,  are  more  reliable, 
and  better  adapted  to  those  cases  where  the  spaces  between  the 
teeth  are  contracted.  The  following  description  of  the  method 
of  constructing  them  is  given  by  Professor  Wild  man.* 

"First  bend  the  clasp  to  fit  the  tooth  accurately;  then 
make  the  attachment  by  which  it  is  to  be  held  to  the  rubber 
(this  may  be  done  by  soldering  a  thin  plate  of  gold  or  platina 

*  Instructions  in  Vulcanite,  p.  3G. 
24 


370  MECHANICAL   DENTISTRY. 

to  the  clasp  in  such  a  position  that  it  will  be  inclosed  in  the 
rubber) ;  then  perforate  the  plate  with  numerous  small  holes, 
which  should  be  countersunk  on  both  sides  (Fig.  147).  This 
plate  entering  the  base,  the  rubber  tilling  the  holes  forms  pins 
which  rivet  the  clasp  securely  to  the  rubber  plate. 

"  Or  the  attachment  may  be  made  in  this  manner :  On  the 
parts  of  the  clasp  that  can  be  covered  with  rubber,  drill  one, 
two,  or  three  holes,  as  the  space  may  admit ;  insert  gold  or 
platina  wire,  solder  with  gold  solder,  then  cut  off  at  proper 
length,  and  head  them  (Fig.  148) ;  these  act  in  retaining  the 
clasp  in  the  same  manner  as  the  double-headed  pins  in  securing 
the  tooth  to  the  base,  and  offer  the  advantage  over  the  perfo- 
rated plate  of  being  more  easily  manipulated,  and  less  liable  to 
become  displaced  in  packing  the  mould.     The  clasp  is  to  be 

Fig.  147.  Fig.  148. 


attached  to  the  model  plate,  and  will  remain  secured  in  the 
mould  when  it  is  opened." 

A  metallic  clasp  may  also  be  very  securely  attached  to  the 
rubber  by  drilling  a  number  of  holes  in  that  part  of  the  clasp 
Avhich  lies  in  contact  with  the  rubber,  and  countersinking  them 
well  on  the  inside  of  the  clasp. 

Substitution  of  Plate  for  Rubber  Teeth. — An  ordinary  plate 
tooth,  such  as  is  commonly  used  in  connection  with  a  metallic 
plate  base,  can  be  readily  rendered  suitable  for  a  rubber  base. 
This  is  done  by  soldering  a  narrow  strip  of  gold  plate  to  the 
ends  of  the  platina  pins,  forming  a  loop  or  staple  (Fig.  149), 
and  which  imbedded  in  the  rubber,  renders  the  attachment 
very  secure.  A  narrow  arm  of  rubber  extending  to  a  single 
tooth  may  be  materially  strengthened  by  permitting  the  gold 
strip,  perforated  with  holes  or  roughened  on  its  edges,  to  pass 
some  distance  into  the  rubber  as  seen  in  Fig.  150. 


VITLCAXITE   BASE.  371 

Instead  of  forming  a  loop  or  staple  as  mentioned,  it  will  be 
preferable  in  many  cases  to  solder  to  the  tooth  a  somewhat 
wider  strip  than  that  represented,  in  the  same  manner  as  ordi- 
narily practiced  in  backing  for  gold  work,  the  strip  being 
strengthened  by  flowing  solder  at  the  angle  of  divergence  from 
the  heel  of  the  tooth,  and  extending  thence  into  the  body  of 
the  rubber,  perforated  or  roughened  on  the  edges  as  before 
recommended.  The  rubber  in  this  case  may  be  cut  away,  when 
finishing,  to  the  angle,  leaving  nothing  but  the  strip  of  gold  and 
sub-linino;  of  rubber  at  the  base  of  the  tooth.  This  method 
may  be  resorted  to  with  signal  advantage  in  those  cases  where, 

Fig.  149.  Fig.  150. 


on  closure  of  the  jaws,  the  points  of  the  opposing  teeth  encroach 
unduly  upon  the  space  to  be  filled,  extending  nearly  to  the 
gum,  requiring  the  tooth  of  replacement  as  thinly  formed 
throughout  its  length  as  possible. 

Repairing. — If  a  tooth  or  block  has  been  broken,  or  any 
change  is  to  be  made  in  the  position  of  either,  the  teeth  or 
fragments  thereof,  are  removed  and  an  irregularly  shaped 
groove  or  dove-tail  formed  in  the  base  occupying  the  space  to 
be  supplied ;  into  this  space  the  tooth  or  teeth  are  properly 
arranged  and  supported  with  wax ;  the  dovetail  is  then  filled 
in  with  wax,  giving  some  additional  fulness  to  compensate  for 
waste  in  finishing.  All  portions  of  the  piece  except  the  lin- 
gual face  of  the  plate  and  teetli  are  then  imbedded  in  plaster 
in  the  lower  section  of  the  flask.  The  upper  section  of  the 
mould  is  obtained  in  the  usual  way.  AV^hen  separated  and  all 
traces  of  wax  removed,  the  gum  is  packed  into  the  cavity 
around  the  tooth  or  teeth.  Grooves  are  then  cut  extending 
out  from  the  mould  ;  the  two  sections  heated  and  forced  to- 
gether, and  the  process  of  vulcanizing  conducted  in  the  usual 
manner,  the  same  time  and  degrees  of  heat  being  required  as 


372  MECHANICAL   DENTISTRY. 

in  the  first  instance.  The  renewed  heat  employed  renders  the 
surface  of  the  material  previously  vulcanized  somewhat  darker, 
to  remove  which  it  is  recommended  to  moisten  the  surface 
with  dilute  nitric  acid  for  a  short  time,  after  which  the  piece 
is  thoroughly  washed  and  then  placed  for  a  few  minutes  in  an 
alkaline  solution  to  remove  any  remaining  traces  of  acid.  It 
is  also  recommended  to  immerse  the  case  in  alcohol  for  five  or 
six  hours,  and  then  expose  it  to  the  rays  of  the  sun  for  a  like 
period  of  time. 

Refitting  Gold  or  Rubber  Plates  with  Rubber  Lining. — Gold 
or  rubber  plates,  whose  adaptation  to  the  mouth  has  become 
impaired,  in  a  greater  or  less  degree,  by  subsequent  absorption 
of  the  alveolar  ridge,  may  be  easily  refitted  and  the  adaptation 
restored  by  either  of  the  following  methods  : 

First  Method. — Take,  for  example,  a  full  upper  set  on 
either  gold  or  vulcanite.  Secure,  in  the  first  place,  an  accu- 
rate impression  of  the  mouth,  in  its  changed  condition,  in 
plaster,  and  from  this  a  plaster  model  in  the  manner  usually 
practiced.  Perforate  the  palatal  portion  of  the  plate  with 
from  eight  to  twelve  holes  at  different  points,  and  also  the  ex- 
ternal borders,  from  heel  to  heel  of  the  plate,  at  intervals  of 
from  one-eighth  to  half  an  inch  apart,  and  near  the  edges. 
These  holes  may  be  enlarged  to  the  dimensions  of  a  medium- 
sized  knitting-needle;,  or  if  the  piece  is  of  vulcanite,  to  twice 
or  three  times  that  size.  On  the  lingual  and  buccal  surfaces 
the  holes  are  well  countersunk  with  a  burr  drill.  The  plaster 
model,  with  the  central  portion  raised  to  form  a  chamber  (and 
which  should  be  made  to  correspond,  as  nearly  as  possible,  in 
position,  form,  and  thickness,  with  the  chamber  in  the  plate, 
if  one  exists),  is  next  heated  throughout  by  placing  it  over  a 
spirit-flame,  or  in  the  baking  furnace  of  an  ordinary  cooking 
stove,  or  the  muffle  of  a  furnace,  and  when  of  a  temperature 
that  will  barely  admit  of  being  taken  in  the  hand,  remove  and 
cover  the  face  of  it  with  a  sheet  of  india-rubber  or  gutta- 
percha as  prepared  for  vulcanite  work,  and  press  it  down  upon 
the  face  of  the  model  with  the  fingers.  Apply  the  perforated 
plate  to  the  model,  being  careful  to  secure  a  proper  relation  of 


VULCANITE   BASE.  373 

the  two ;  then  press  the  former  down  firmly  upon  the  model. 
To  render  the  vulcanite  material  still  more  plastic  and  com- 
pressible, the  whole  may  now  be  returned  to  the  furnace,  and 
subjected  to  a  uniform  heat  throughout,  when  it  may  be  re- 
moved, and  firm  and  steady  pressure  made  upon  the  plate  and 
teeth,  until  forced,  as  nearly  as  practicable,  into  contact  with 
the  face  of  the  model.  Portions  of  gum  will  be  forced  through 
the  apertures  and  out  at  the  borders  of  the  plate ;  these  should 
be  well  packed  into  the  countersinks  and  under  the  edges  of 
the  plate,  when  the  model,  with  the  rubber  and  plate  adherent, 
may  be  placed  in  a  vulcanizing  flask  and  incased  bodily  in 
plaster.  It  is  tlien  placed  in  a  heater  and  vulcanized.  If  all 
the  steps  in  the  process  have  been  carefully  conducted,  the  fit 
of  the  plate  will  be  perfectly  restored,  with  no  material  change 
in  the  antagonism,  or  none,  at  least,  that  is  not  susceptible  of 
ready  correction.  The  union  between  the  vulcanite  lining  and 
the  plate  will  be  strong  and  lasting,  and  altogether  imperme- 
able to  the  fluids  of  the  mouth. 

In  the  case  of  lower  pieces,  the  holes  should  be  made  along 
the  external  and  internal  borders  of  the  plate  near  the  margins. 
In  all  other  respects  the  manipulations  are  the  same  as  those 
described  above. 

It  is  scarcely  necessary  to  observe  that,  in  the  use  of  gold 
plates,  the  method  is  inapplicable  whenever  it  is  designed  to 
re-swage  the  same  plate  for  the  permanent  piece. 

Second  Method. — Perforate  the  plate,  whether  of  gold,  silver, 
or  vulcanite,  as  before  directed ;  and  employing  this  as  a  cup 
or  holder,  take  an  impression  of  the  mouth  in  plaster,  pressing 
the  plate  up  closely  to  the  parts.  The  plaster  forced  through 
the  holes,  and  filling  the  countersinks  on  the  opposite  side  of 
the  plate,  will  serve  to  bind  the  plaster  to  the  plate,' and  pre- 
vent, with  cautious  manipulation,  the  two  from  separating  as 
they  are  being  detached  from  the  mouth.  When  removed,  the 
piaster  impression  lining  the  plate  is  trimmed  even  with  the 
borders  of  the  latter,  and  then  varnished  and  oiled.  The  lower 
section  of  a  vulcanizing  flask  is  now  filled  with  a  batter  of 
plafiter  on  a  level  with  its  upper  surface,  and  the  impression, 


374  MECHANICAL,   DENTISTRY. 

filled  with  the  same,  is  turned  over  and  placed  in  the  centre  of 
the  flask,  with  the  edges  of  the  plate  touching  the  surface  of  the 
plaster.  The  plate  and  adhering  plaster  are  now  carefully 
separated  from  the  model.  After  cutting  out  the  plaster  from 
the  holes  and  countersinks  in  the  plate,  the  plaster  forming  the 
impression  is  detached  from  the  plate,  and  the  holes  and  coun- 
tersinks filled  with  wax.  The  plate  is  then  readjusted  over 
the  model,  and  (the  surrounding  surface  of  the  plaster  in  tlie 
flask  liaving  been  varnished  and  oiled)  plaster  is  poured  in 
upon  the  upper  surface  of  the  plate  and  teeth,  filling  the  upper 
ring.  When  the  plaster  is  sufliciently  hard,  the  two  sections 
of  the  flask  are  separated,  and  grooves  formed,  running  out 
from  the  matrix  to  the  margins  of  the  flask.  A  sufficient 
quantity  of  vulcanizable  rubber  is  now  either  placed  upon  the 
model  or  packed  in  upon  the  palatal  surface  of  the  plate — 
before  doing  which,  however,  the  Avax  filling  the  holes  and 
countersinks  in  the  plate  (and  which  was  placed  there  to  pre- 
vent portions  of  plaster  last  poured,  in  forming  the  matrix, 
from  running  in  and  filling  them  up)  should  be  worked  out 
with  a  small  instrument.  The  whole  being  sufficiently  heated, 
the  two  sections  of  the  flask  are  forced  together,  expelling  re- 
dundant material.  The  piece  is  then  vulcanized  as  in  the 
former  case. 

The  above  method,  though  somewhat  more  complicated  than 
the  former,  is  quite  simple  in  its  details,  and  will  occupy  but 
little  more  time,  and  is,  withal,  more  certain  in  its  results. 

Manner  of  Duplicating  Sets  of  Teeth  Mounted  on  Rubber. — 
When  from  accident,  or  other  causes,  a  rubber  set  becomes 
broken,  or  its  integrity  otherwise  impaired,  necessitating  an 
entirely  ilew  plate  with  an  exact  reproduction  of  the  arrange- 
ment and*  articulation  of  the  teeth,  the  following  method,  de- 
scribed by  Professor  Wildman,  may  be  pursued  with  an  absolute 
certainty  of  success.  "  Roughen  the  palatal  surface  of  the  rubber, 
to  cause  the  plaster  to  adhere  to  it ;  then  use  it  as  an  impression- 
cup  to  take  a  plaster  impression,  being  careful  when  it  is  in  the 
mouth  to  preserve  the  articulation.  In  this  impression,  cast  the 
model,  trim,  cut  keys  or  conical  holes  at  several  points  in  its  outer 


VULCANITE  :base.  375 

face,  Xow,  before  separating  the  impression  from  the  model, 
make  a  cast  of  the  face  of  the  teeth  in  two  or  three  perpendicular 
section?,  extending  to  the  base  of  the  model,  using  a  solution  of 
soap  or  other  parting  substance  on  the  plaster  mould.  Remove 
this  mould  of  the  face  of  the  teeth,  which  indicates  their  true 
position  relative  to  the  model ;  then  take  the  impression  from 
the  model.  By  the  aid  of  heat  sufficient  to  soften  the  rubber, 
remove  the  teeth  from  it.  Next  make  a  model  plate  with  pre- 
pared gutta-perclia.  Now  secure  the  section  of  the  mould  of 
the  face  of  the  teeth  to  the  model  (their  place  will  be  indicated 
by  the  keys);  adjust  the  teeth  to  their  proper  positions  in  the 
plaster  mould  of  them,  and  build  up  with  gutta-percha  or  wax 
to  the  proper  form  of  the  model  set.  This  being  done,  test  its 
accuracy  of  contour  and  articulation  by  placing  it  in  the  mouth. 
Then,  using  the  model,  proceed  as  for  making  a  new  set." 

It  will  be  observed  that  the  above  process  contemplates  the 
necessity  of  the  patient's  presence  to  secure,  in  the  first  instance, 
an  impression  of  the  mouth,  and  again  for  a  trial  of  the  teeth 
in  the  mouth  to  test  the  accuracy  of  arrangement,  etc.  This 
procedure  is  rendered  necessary  in  all  cases  of  faulty  adapta- 
tion of  the  primary  plate,  but  where  the  adaptation  is  satisfac- 
tory, and  it  is  desired  to  construct  a  duplicate  set  in  all  respects 
precisely  like  the  original,  the  following  method,  in  the  main 
the  same  as  the  one  just  described,  may  be  adopted  in  the 
absence  of  the  patient.  Oil,  or  coat  with  a  solution  of  soap, 
the  palatal  surface  of  the  plate  to  be  duplicated  ;  into  this  pour 
plaster  for  the  model ;  trim  to  the  edges  of  the  plate,  and  give 
the  usual  form  to  the  body  of  the  model;  form  conical  holes 
in  the  same  and  secure  sectional  moulds  of  the  outer  faces  of 
the  teeth  in  the  manner  described  by  Professor  Wildman. 
When  hard,  remove  these  se(  tlons  and  detach  the  model  from 
the  plate.  Many  cases  will  admit  of  a  ready  separation  ;  in 
others  it  will  be  found  impossible  to  force  them  apart  without 
fracturing  the  model.  To  avoid  such  an  accident,  the  model 
may  Ijc  ciust  in  sections,  the  latter  being  bound  together  after- 
wards in  their  proper  relation  to  each  other.  But  a  better 
])lan   is  to  heat  the  model  and  plate  sufficiently  to  render 


376  MECHANICAL   DENTISTRY. 

the  rubber  soft  and  pliant  enough  to  be  removed  without 
injury  to  the  model.  Cases  not  admitting  of  the  successful 
application  of  either  of  these  expedients  must  be  treated  in  the 
manner  described  by  Professor  Wildman,  that  is,  by  securing 
an  impression  of  the  mouth.  After  the  separation  of  the 
model  and  plate,  the  manner  of  conducting  the  subsequent 
steps  of  the  operation  is  precisely  the  same  as  that  described  in 
the  preceding  method.  The  author  has  adopted  the  above  pro- 
cess in  a  number  of  instances  with  the  most  gratifying  success 
in  cases  of  defects  or  accidents  to  the  original  plate,  and  where 
the  presence  of  the  patient  could  not  be  conveniently  com- 
manded. 


CELLULOID    BASE.  377 


CHAPTER  XV. 
Celluloid  Base. 

The  employment  of  celluloid  in  prosthetic  dentistry,  though 
of  recent  date,  and  notwithstanding  the  very  general  failure 
■which  attended  its  first  introduction  into  practice,  is  rapidly 
acquiring  very  general  professional  favor  as  a  cheap,  conve- 
nient, and  serviceable  base  for  artificial  dentures.  With  the 
more  recent  improvements  in  the  manufacture  and  seasoning 
of  blanks,  more  perfectly  adapted  appliances  for  moulding, 
and  a  more  extended  acquaintance  with  the  peculiar  and  dis- 
tinctive characteristics  of  this  material,  it  promises,  in  the 
near  future,  to  supersede  in  a  great  measure  all  other  known 
plastic  substances  for  the  purpose  indicated. 

That  celluloid  possesses  many  important  qualities  M'hich 
commend  its  employment  as  a  base  in  preference  to  rubber  can 
hardly  be  questioned.  It  is  more  in  harmony  w^th  the  soft 
tissues  of  the  mouth,  more  cohesive  in  texture,  fig-  i^i 

approximates  more  nearly  the  natural  gum 
color,  contains  far  less  vermilion  pigment  in 
its  composition,  and  is  less  objectionable  by 
reason  of  the  comparative  cleanliness  accom- 
panying its  manipulation. 

The  chief  objection  urged  against  celluloid  as  a  base  is  its 
low  ])Ower  of  transmitting  caloric,  but  it  is  believed  to  be  less 
objectionable  in  this  respect  than  rubber.  Both  are  poor  con- 
ductors, and  the  soft  tissues  of  the  mouth  in  contact  with  either 
suffer,  in  some  degree,  as  a  consequence  of  this  property.  To 
obviate,  to  some  extent  at  least,  this  objectionable  feature  of 
both  rubber  and  celluloid,  Dr.  S.  C.  Carter  has  devised  and 
recommended  what  is  termed  "  palate  coolers,"  consisting  of  a 


378  MECHANICAL   DENTISTEY. 

central  plate   of  either  gold,  platinum,  or   aluminum,  dove- 
tailed into  the  rubber  or  celluloid,  and  represented  in  Fig.  151. 

Celluloid,  as  at  present  produced,  and  when  properly  ma- 
nipulated, does  not,  in  any  appreciable  degree,  undergo  change 
of  form  after  moulding  by  warping  either  in  or  out  of  the 
mouth,  as  was  formerly  the  case,  nor,  it  is  believed,  does  it 
absorb  the  oral  secretions.  It  loses  somewhat  the  freshness 
and  clearness  of  its  original  pink  color  after  having  been  in 
use  for  some  time,  but  not  in  any  very  marked  degree. 

Though  not  bearing  so  perfect  a  resemblance  to  the  com- 
plexion of  the  healthy  gum  tissue  as  the  porcelain  imitations, 
yet  the  near  approximation  of  celluloid  to  the  desired  color 
makes  the  use  of  single  plain  teeth  admissible  for  permanent 
dentures,  and  this  is  unquestionably  its  crowning  merit,  and 
makes  it  the  most  desirable  of  all  the  so-called  "  cheap  bases." 
The  indiscriminate  and  almost  universal  employment  of  block 
or  sectional  gum  teeth  in  connection  with  rubber  has,  it  may  be 
safely  affirmed,  done  more  to  degrade  the  prosthetic  department 
of  dental  practice  than  all  other  causes  combined.  The  optional 
arrangement  of  each  individual  tooth  to  meet  the  requirements 
of  special  cases  in  respect  to  expression,  articulation,  and  an- 
tagonism is  one  of  the  absolute  and  indispensable  requirements 
of  a  perfect  artificial  denture.  A  more  general  recognition  of 
this  important  fact  must,  sooner  or  later,  lead  to  the  entire 
abandonment  of  rubber  in  connection  with  "  ready-made " 
sectional  gum  teeth.  "  Taking  into  view  all  its  qualities,"  says 
a  well-known  writer,  "  and  leaving  out  the  question  of  freedom 
from  monopolies,  the  conclusion  is  that  celluloid  has  the 
potentialities  which  should  dethrone  rubber,  and  establish  itself 
as  the  best  of  the  cheap  bases." 

Composition  and  Manufacture. — The  following  is  the  sub- 
stance of  Professor  Charles  J.  Essig's  account  of  the  composition 
and  manufacture  of  celluloid  : 

Celluloid  is  derived  from  cellulose,  a  woody  fibre,  constitut- 
ing the  framework  or  foundation  of  j)lants. 

Linen,  cotton-wool,  hemp,  etc.,  are  examples  of  cellulose. 
For  the  manufacture  of  celluloid,  the  cellulose  is  first  converted 


CELLULOID    BASE.  379 

into  paper ;  hemp  is  the  form  of  cellulose  employed  for  this 
purpose,  because  it  has  been  found  to  make  the  strongest  paper, 
and  the  stronger  the  paper  the  better  the  celluloid. 

The  hemp  is  first  converted  into  paper  in  the  usual  way  by 
paper  machines.  By  this  process  the  form  of  the  material 
undergoes  a  physical  change  only,  while  chemically  it  remains 
the  same,  viz.,  nearly  pure  cellulose,  and  has  a  formula  of 
CgHioOj.  The  cellulose,  now  in  the  form  of  hemp-paper,  is 
converted  into  pyroxylin  by  a  process  technically  known  as 
"conversion,"  this  change  being  effected  by  immersing  the 
hemppaper  in  a  strong  mixture  of  nitric  and  sulphuric  acids 
for  a  sufficient  length  of  time,  when  it  is  removed  from  the 
acids  and  washed  thoroughly. 

It  is  now  still  in  the  form  of  paper,  but  its  weight  will  be 
found  to  have  increased  about  seventy  per  cent.,  and  to  have 
become  highly  explosive,  taking  fire  at  about  300°  F. 

Pyroxylin,  then,  is  the  chief  ingredient  in  celluloid,  and  is 
reduced  to  a  pulp  in  a  machine  similar  to  that  used  in  paper- 
making  ;  a  thorough  mixture  is  then  made  of 

Pyroxylin, 100  parts 

Camphor,       .         .         .       ' 40     " 

Oxide  of  zinc, 2     ' 

Vermilion,     .' 0.6 

Some  alcohol  is  used  to  soften  the  camphor.  The  mass  is 
now  put  under  a  hydraulic  pressure  of  two  thousand  pounds  to 
the  square  inch.  The  cylinders  in  which  it  is  pressed  have  a 
small  orifice  in  the  side  near  the  bottom,  and  when  pressure  is 
made  the  celluloid  is  forced  out  through  this  orifice. 

The  immense  pressure  is  to  condense  or  solidify  the  cellu- 
loid, and  as  it  is  forced  out  it  is  cut  off  in  pieces  of  the  proper 
size,  and  moulded  by  pressure  and  heat  to  the  forms  in  which 
we  receive  it.  At  this  point  the  blanks  are  still  soft,  and  require 
to  be  seasoned;  this  requires  ai)out  two  months,  during- which 
time  they  are  kept  in  a  room  at  a  temperature  of  1G0°  F. 


380  MECHANICAL   DENTISTEY. 

Processes  Preliminary  to  Moulding. 

While  many  of  the  processes  entering  into  the  construction 
of  artificial  dentures,  with  celluloid  as  a  base,  are  essentially 
the  same  as  those  required  when  rubber  is  used,  yet  there  are, 
in  many  important  respects,  modifications  of  practice  made 
necessary  by  the  peculiar  nature  and  behavior  of  the  material 
employed. 

When  the  distinctive  characteristics  of  celluloid  are  well 
understood,  and  the  operator  is  familiar  with  the  approved 
methods  of  working  it,  no  unusual  difficulties  attend  its  success- 
ful manipulation.  To  attain  uniform  and  satisfactory  results, 
however,  it  is  absolutely  necessary  that  there  should  be  a  faith- 
ful compliance  with  every  manipulative  detail,  however  seem- 
ingly unimportant,  which  experience  in  the  use  of  this  substalice 
has  demonstrated  to  be  essential. 

Plaster  Model. — The  inferior  plasticity  of  celluloid,  compared 
with  vulcanizable  rubber,  when  exposed  to  the  action  of  heat, 
and  the  consequent  greater  pressure  necessary  to  mould  it  into, 
any  given  form,  makes  it  necessary  to  give  to  the  plaster  model 
the  greatest  practicable  hardness  and  strength.  To  secure  these 
important  qualities,  it  is  recommended  to  use  the  best  quality 
of  coarse  builder's  plaster,  which,  though  it  does  not  set  so 
quickly  as  the  finer  and  whiter  varieties,  becomes  much  harder 
and  more  resistant  to  pressure  when  thoroughly  dried.  In- 
creased hardness  will  be  secured  by  adding  to  the  plaster  mix- 
ture a  small  quantity  of  clean  white  river  or  lake  sand  or 
marble  dust. 

A  smoother  face  will  be  given  to  the  model  by  first  coating 
the  surface  of  the  impression  with  a  moderately  thin  mixture 
of  fine  plaster,  and,  as  this  begins  to  set,  fill  in  with  the  coarser 
variety  for  the  body  of  the  model. 

The  plaster  for  the  model  should  be  mixed  as  thick  as  can 
be  well  poured,  taking  care,  as  it  is  slowly  introduced,  to  expel 
air-bubbles  by  tapping  or  shaking  the  impression-tray  as  the 
plaster  flows  in. 

In  cases  where  there  is  any  considerable  anterior  projection 


CELLULOID   BASE.  381 

of  the  alveolar  ridge  in  front,  above  or  below,  the  correspond- 
ing portion  of  tlie  plaster  model  is  liable  to  be  crushed  under 
the  pressure  necessary  to  mould  celluloid.  To  prevent  such 
accident,  it  has  been  recommended,  in  addition  to  the  expedient 
to  be  mentioned  hereafter,  to  place  in  the  front  part  of  the  im- 
pression a  curved  piece  of  brass  plate  punched  full  of  holes, 
one-half  or  three-fourths  of  an  inch  wide,  which,  when  the 
impression  is  filled,  will  be  imbedded  in  the  central  portion  of 
the  plaster  ridge,  and  extend  some  distance  into  the  body  of 
the  model. 

In  extreme  cases,  where  the  ridge  is  very  thin  and  the  pro- 
jection spoken  of  excessive,  it  may  be  necessary  to  substitute 
metal  for  plaster  in  forming  the  model.  In  this  case  the  latter 
may  be  obtained  by  pouring  block-tin  or  Babbitt  metal  directly 
into  the  plaster  impression,  which  should  first  be  thoroughly 
dried,  and  the  cavity  for  the  air-chamber  formed  before 
pouring. 

Waxing. — After  having  arranged  the  teeth  for  any  given 
case,  place  them  with  the  trial  plate  on  the  model,  and  build 
out  with  wax  to  the  required  form,  but  a  little  in  excess  of  the 
fulness  necessary  in  the  finished  piece.  Care  should  be  taken 
that  the  palatal  portion  should  be  somewhat  thinner  than  the 
blank  to  be  used.  Clean,  pure  wax  should  always  be  used  in 
preparing  a  case  for  flasking,  as  it  will  be  necessary  some- 
times to  free  the  mould  of  adhering  and  inaccessible  portions 
with  boiling  water,  in  which  case,  if  there  are  impurities  in 
the  wax,  sedimentary  particles  will  be  left  in  the  mould  and 
become  incorporated  with  the  celluloid  in  the  process  of 
moulding. 

Investing. — The  piece  prepared  as  above  is  then  placed  in  a 
flask  especially  designed  for  ceHuloid,  invested  in  plaster,  and 
the  mould  or  matrix  formed  in  the  same  manner  as  practiced 
when  rubber  is  used.  In  case  the  ridge  overhangs,  to  which 
the  term  "  under-cut "  is  applied,  the  model,  before  being 
incased  in  the  flask,  should  be  cut  across  diagonally  with  the 
slope  towards  the  heel  of  the  model,  thus  depressing  the  latter 


382 


MECHANICAL   DENTISTRY. 


posteriorly,  as  exhibited  in  Fig.  152.  By  this  means  the  pro- 
jecting portion  of  the  ridge  will  be  brought  more  directly  in  a 
line  Avith  the  pressure  in  closing  the  flask. 

It  is  quite  as  important  that  the  incasing  plaster  forming 
the  matrix  should  be  as  hard  and  resistant  to  pressure  as  that 
entering  into  the  composition  of  the  plaster  model.  If  this 
condition  is  not  secured  there  will  be  great  danger,  not  only 
of  fracture  of  the  model  for  the  want  of  adequate  lateral  sup- 
port, but  of  displacement  of  the  teeth  by  being  forced  into  the 
plaster.  So  important  is  the  right  condition  and  manipula- 
tion of  plaster  in  the  use  of  celluloid  that  the  author  feels  war- 


FlG.  152. 


ranted  in  adding,  to  what  has  already  been  said  in  this  connec- 
tion, the  following  judicious  comments  contained  in  a  pamphlet 
issued  by  the  manufacturers  of  celluloid  : 

"  Plaster  should  always  be  mixed  as  thick  as  possible,  and, 
if  convenient,  allowed  to  set  over  night,  with  the  flask  open, 
and  dried  in  a  warm  place,  as  it  is  thereby  rendered  much 
harder.  Simple  as  the  operation  is,  comparatively  few  under- 
stand how  to  mix  plaster  so  as  to  get  the  greatest  strength  and 
resistance  to  pressure.  The  proper  way  to  mix  plaster  for 
both  models  and  filling  flasks  is  as  follows:  First,  stir  up 
some  plaster  as  thick  as  can  be  well  poured,  taking  care  that 
there  is  no  excess  of  water;  pour  some  of  this  into  the  flask  or 
impression  to  be  filled,  and  shake  down  well.  Then,  into 
what  remains  in  the  bowl,  stir  more  plaster  until  you  have  a 
mass  so  thick  that  it  can  be  piled  up.  With  this  the  flask  is 
filled  up  and  thoroughly  shaken  down.     It  is  surprising  how 


CELLULOID    BASE.  383 

much  plaster  can  be  stirred  in  after  the  first  is  poured  out,  and 
also  how  a  thick  mass,  such  as  described,  will  settle  down  in 
the  flask  without  bubbles.  The  thinner  plaster  first  poured 
in  will  run  and  be  driven  by  the  thicker  afterwards  added, 
into  all  the  crevices,  and  most  of  it  will  escajie  from  the  flask, 
leaving  a  body  of  solid,  resisting  plaster  that  cannot  be  ob- 
tained by  the  ordinary  method  of  mixing." 

AVhen  the  piece  is  incased,  and  the  plaster  has  sufficiently 
hardened,  the  two  sections  of  the  flask  should  be  carefully 
separated,  and  this  can  be  done  with  greater  safety  to  the 
model  and  other  portions  of  the  matrix,  and  with  less  liability 
of  loosening  and  detaching  the  teeth  from  the  plaster,  by  first 
applying  just  sufficient  heat  to  the  flask  to  soften  the  wax  and 
trial  plate,  being  careful  not  to  melt  the  wxix  by  too  great  or 
long-coiitinued  heat. 

When  the  flask  is  separated,  all  portions  of  wax  or  other 
material  should  be  carefully  and  thoroughly  removed  from 
the  mould,  and  if  any  remain  not  accessible  to  instruments,  the 
section  or  sections  of  the  flask  containing;  remains  of  wax 
should  be  placed  in  a  clean  vessel  under  clean  water  and  wel^ 
boiled  until  all  is  expelled.  The  thin,  frail  edges  encircling 
the  matrix  in  both  sections  of  the  flask  should  then  be  cut 
away  somewhat,  and  well  rounded  to  prevent  fracture  and 
consequent  mixing  of  particles  of  plaster  with  the  celluloid  in 
moulding.  AVhen  this  is  done,  put  the  flask  together  and  see 
if  there  is  ample  room  for  the  "  jiose"  of  the  model  to  pass  the 
edge  of  the  matrix. 

To  permit  the  escape  of  surplus  material  in  moulding,  either 
of  the  following  plans  may  be  adopted  :  1.  Cut  two  concen- 
tric grooves  in  tlie  plaster  of  the  upper  or  lower  section  com- 
pletely encircling  the  matrix,  the  inner  one  not  less  than  one- 
fourth  or  one-sixth  of  an  inch  from  the  mary-in  of  the  mould, 
and  the  other  at  the  border  of  the  flask,  the  inner  side  of  the 
latter  forming  a  part  of  the  outer  groove.  2,  Bevel  the  plaster 
around  the  jnould,  commencing  about  one-fourth  of  an  inch 
from  the  margins  of  the  latter  and  extending  it  to  the  sides  of 
the  flask.    3.  (Jut  cone-shaped  cross  or  radiating  grooves  from 


384  MECHANICAL   DENTISTEY. 

the  inner  circular  gutter  to  the  margins  of  the  flask, — shallow 
where  they  connect  with  the  circular  groove,  and  deepening 
and  widening  towards  the  edges  of  the  flask. 

In  no  case  should  cross  grooves  be  made  communicating 
with  the  matrix,  as  these  aiford  too  ready  an  exit  for  surplus 
material,  and  prevent  that  "  back  pressure "  so  essential  to  a 
complete  and  compact  filling  of  the  mould.  The  grooves 
should  be  deep  and  ample  enough  to  receive  all  surplus,  other- 
wise it  will  be  diflicult  if  not  impossible  to  close  the  flask  per- 
fectly. In  the  use  of  gum  teeth,  holes  may  be  drilled  in  the 
matrix  inside  tlie  teeth,  opposite  each  joint,  not  over  an  eighth 
of  an  inch  in  diameter,  and  as  deep  as  it  may  be  deemed  neces- 
sary. These  act  as  waste  gates,  and  relieve  the  blocks  from 
pressure. 

Selection  and  Preparation  of  the  Celluloid  Plate  or  Blank. — 
The  mould  having  been  prepared  in  the  manner  described,  a 
suitable  blank  should  be  selected,  and,  as  it  is  important  that 
this  should  be,  as  nearly  as  possible,  the  size  and  general  form 
of  the  mould,  a  good  assortment  of  plates,  for  both  entire  and 
partial  pieces,  should  be  at  command  from  which  to  select  for 
any  given  case.  Special  attention  is  directed  to  this  important 
requirement.  Celluloid  does  not,  like  rubber,  flow  together 
and  intimately  intermix  when  exposed  to  heat  and  pressure. 
If,  therefore,  the  blank  is,  in  any  considerable  degree,  wider 
than  the  model,  or  its  central  or  palatal  portion,  fuller  and 
deeper  than  that  of  the  model,  the  material,  when  under  pres- 
sure, will  lap  or  fold  upon  itself  along  the  lateral  walls  of  the 
arch,  and,  failing  to  unite,  will  form  grooves  or  fissures.  On 
the  other  hand,  if  it  is  not  wide  or  deep  enough,  the  material 
is  liable  to  be  stretched  and  torn.  The  blank  should  be  just 
large  enough  to  fill  all  parts  of  the  mould  perfectly,  with  some 
slight  excess,  and  the  central  portion  should  always  be  some- 
what thicker  than  the  corresponding  part  of  the  trial  or  pattern 
plate. 

As  celluloid  cannot  be  depended  on  to  flow  from  one  part  of 
the  mould  to  another,  it  is  important  that  there  should  not  only 
be  an  excess  of  material,  but  that  this  excess  should  be,  as 


CELLULOID    BASE.  385 

nearly  as  practicable,  distributed  throughout  all  portions  of  the 
matrix.  A  neglect  of  this  precaution  will  result  either  in  an 
imperfect  filling  of  the  mould  in  some  places,  and  consequent 
defect  of  the  plate,  or  a  porous  condition  of  the  celluloid  will 
be  found  wherever  the  material,  though  apparently  filling  the 
mould,  has  not  been  impacted  with  sufficient  force. 

The  selected  blank  should  be  conformed  as  nearly  as  pos- 
sible to  the  shape  of  the  mould  by  heating  it  in  boiling  water 
and  pressing  it  with  the  fingers  into  the  section  of  the  matrix 
containing  the  teeth ;  after  which  the  necessary  fulness  of  the 
several  parts  of  the  blank  may  be  obtained  by  dressing  away 
redundant  portions  with  files,  a  small  bracket  saw,  or  the  knife, 
first  softening  the  plate  in  boiling  water  before  using  the  latter. 

Greater  exactness  in  the  required  amount  of  celluloid  neces- 
sary in  any  given  case  may  be  obtained  by  measurement,  the 
simplest  method  being  by  the  use  of  the  Starr  instrument, 
illustrated  in  the  chapter  on  Vulcanite.  It  must  be  remembered, 
however,  that  this  device  onlv  determines  the  ago-regate  amount 
of  material  necessary,  and  that,  while  it  may  be  a  safe  guide 
in  the  use  of  rubber  which  flows  freely,  it  may  lead  to  failure 
when  celluloid  is  employed,  unless  care  is  taken  that  all  parts 
of  the  blank  correspond  with  the  capacity  of  the  mould. 

A  more  reliable,  though  somewhat  tedious,  method  of  secur- 
ing exactness  in  the  quantity  and  distribution  of  material  nec- 
essary, and  which  acquires  special  value  in  cases  where  there 
Ls  unusual  danger  of  fracture  of  the  model  or  teeth,  and  espe- 
cially of  the  latter  when  gum  teeth  are  used  and  these  are 
ground  very  thin,  is  the  following,  given  by  a  correspondent 
of  the  Cosmos :  "  After  preparing  the  case  ready  to  flask, 
remove  the  teeth  from  the  pattern ;  stop  the  pin-holes,  then 
remove  the  pattern  and  carefully  flask  it.  When  the  mould  is 
ready,  remove  all  the  wax  or  material  of  the  pattern;  place 
the  celluloid  '  blank ;'  api)]y  heat,  and  cast  the  same  as  if  for 
final  case.  Remove  the  flask  from  the  heater;  ])]ace  it  in  the 
clamp  and  cool  rapidly.  When  it  is  entirely  cool  remove  it 
from  the  flask,  and  trim  as  carefully  as  for  final  case  until  the 
blank  is  almost  the  same  as  the  pattern  in  thickness  (it  always 

25 


386  MECHANICAL    DENTISTRY. 

comes  out  thicker).  Now  you  have  a  blank  with  but  little  ex- 
cess; only  what  the  vacuum  and  pins  displace,  or  slightly 
more,  and  exactly  the  shape  of  the  pattern,  minus  the  teeth. 
Now  set  up  the  case  again,  being  careful  to  make  the  pattern 
the  same  size ;  flask,  and  when  ready  remove  the  pattern ;  if 
doubtful  as  to  amount  of  excess,  pare  the  edges  of  the  mould 
slightly,  which  will  be  all  that  is  needed.  Replace  the  blank ; 
apply  heat,  when  but  moderate  pressure  will  be  found  neces- 
sary to  bring  the  flask  entirely  together.  If  dry  heat  is  pre- 
ferred, dip  the  edges  of  the  blank  to  come  in  contact  with  the 
pins  in  spirit  of  camphor  for  a  few  minutes  before  casting." 

Before  the  blank  is  placed  in  the  flask  preparatory  to  mould- 
ing, some  provision  should  be  made  against  adhesion  of  the  plas- 
ter to  the  plate.  This  may  be  done  by  oiling  the  surface  of  the 
model,  or  by  coating  it  and  other  portions  of  the  matrix  with 
either  collodion  or  liquid  silex,  or  by  rubbing  the  surfaces  well 
with  French  chalk,  or  powdered  soapstone ;  or  a  layer  of  tin 
foil  may  be  interposed  between  the  model  and  blank.  The  fol- 
lowing novel  method  of  coating  the  surface  of  the  model  with 
tin  is  recommended  by  Charles  P.  Alker,  of  Bordeaux,  France : 
"  Reduce  ordinary  collodion  with  about  three  times  its  bulk  of 
ether,  and  add  powdered  tin  until  the  solution  is  well  impreg- 
nated with  the  metal.  The  tin  is  the  same  that  is  sometimes 
used  for  coating  plaster  images.  When  properly  mixed  and  ap- 
plied with  a  brush,  an  even  covering  of  tin  is  formed  upon  the 
model,  so  dense  as  to  closely  resemble  tin  foil,  and  so  firm  as 
to  not  be  detached  by  boiling  water  or  heat.  The  plate  is  read- 
ily cleansed  with  a  coarse  brush,  and  presents  the  appearance 
of  having  been  made  in  a  metallic  mould." 

The  case,  as  thus  described,  is  now  ready  for  moulding. 

Moulding. — The  various  machines  or  heaters  now  generally 
employed  in  moulding  celluloid  into  dental  plates  contemplate 
the  use  of  either  hot  moist  air,  glycerin,  or  steam  for  the  pur- 
pose of  producing  the  requisite  plasticity  of  the  material  sub- 
jected to  pressure.  There  is  considerable  diversity  in  the  form 
and  construction  of  heaters  designed  to  utilize  these  several 
sources  of  heat,  as  well  as  differences  in  the  modes  of  applying 


CELLULOID    BASE. 


387 


pressure,  and  while  each  has  doubtless  some  special  points  of 
merit  not  possessed  by  others,  satisfactory  results  may,  with 
careful  and  intelligent  manipulation,  be  attained  by  the  use  of 
any  one  of  the  many  recommended.  The  limits  of  this  work 
will  only  permit  the  introduction  of  such  as  are  believed  to  be 
in  most  general  use. 

Hot  2Ioist  Air  (so-called  "Dry  Heat")  Maekines.—ln  the 
use  of  these  heaters,  the  water  with  which  the  plaster  is  im- 


pregnated is  relied  upon  to  produce  the  steam  necessary  to  carry 
off  all  excess  of  camphor  from  the  celluloid  in  the  process  of 
moulding.  An  easential  point  by  this  method  is  to  have  the 
plaster  in  the  flask  thoroughly  wet,  and  this  may  be  better  at- 
tained by  setting  the  flask  in  a  vessel  of  water  before  placing 
it  in  the  heater.  To  provide  against  insufficiency  of  moisture 
in  the  plaster,  a  sn)all  quantity  of  water  may  be  introduced 
into  the  tank  before  applying  lieat. 

Fig.  153  represents  a  moulding  or  packing  machine  of  the 


388  MECHANICAL  DENTISTRY. 

class  here  spoken  of,  and  is  designated  as  the  "  Best."*  The 
inside  chamber  is  of  cast  iron,  surrounded  by  a  sheet-iron 
casing.  The  lid,  of  cast  iron,  forming  a  part  of  the  clamp,  is 
pierced  for  the  passage  of  three  wrought-iron  screw-bolts, — 
the  nuts  being  on  the  upper  side  and  easy  of  access.  When 
these  nuts  are  turned  for  the  purpose  of  closing  the  clamp,  the 
bottom  portion  of  the  clamp  is  drawn  up  by  each  revolution 
away  from  the  flame,  thus  avoiding  the  danger  of  overheating 
the  plate,  and  securing  a  uniform  heat.  The  bottom  of  the 
cast-iron  chamber  and  the  lid  are  pierced  with  holes,  to  allow 
a  circulation  through  the  chamber,  for  the  purpose  of  carry- 
ing off  the  camphor  which  is  disengaged  in  the  process. 

With  the  celluloid  blank  adjusted  to  its  proper  position  in 
the  flask,  the  latter  is  placed  in  the  clamp  and  the  top  screwed 
down  until  it  slightly  presses  the  flask.  It  is  then  placed  in 
the  oven  or  tank,  and  heat  applied. 

If  gas  is  used,  the  form  of  burner  shown  underneath  the 
heater  in  Fig.  153,  which  gives  a  pure,  blue  flame  without 
smoke,  may  be  used.  If  gas  cannot  be  commanded,  however, 
any  of  the  alcohol  or  kerosene  lamps  commonly  employed  in 
vulcanizing  may  be  substituted ;  or,  the  "  Hot  Blast  Oil  Stove," 
especially  adapted  to  the  "  Best "  machine,  and  exhibited  in 
connection  with  the  latter  in  Fig.  154,  and  its  construction  in 
detail  shown  in  sectional  diagram.  Fig.  155,  will  be  found 
convenient  and  efficient. 

Having  applied  the  heat,  it  is  of  the  first  importance  that 
unremitting  attention  should  be  given  to  the  process  of  mould- 
ing until  it  is  completed.  If  pressure  is  applied  before  the 
celluloid  is  rendered  somewhat  plastic,  or  too  great  force  is  ex- 
erted during  the  earlier  stages  of  the  process,  and  without  suf- 


*  Among  other  approved  machines,  applicable  to  the  so-called  "  dry  heat " 
process,  may  be  mentioned  "  Brown's  "  and  "  Hays's  "  celluloid  apparatus, 
provided  with  screw-bolts  similar  to  the  "  Best,"  the  Hays  heater  being 
used  in  connection  with  the  Hays  or  Whitney  boiler ;  the  "  Hindsman 
Heater ;"  a  "  Celluloid  Press "  manufactured  by  Spencer  and  Crocker,  of 
Cincinnati,  and  doubtless  others  with  which  the  author  is  unacquainted. 
All  of  these,  except  the  "Hindsman"  Heater,  are  adapted  to  either  dry 
heat  or  glycerin. 


CELLULOID   BASE. 


389 


fiolent  intervals  of  rest,  there  is  danger  of  crushing  or  fractur- 
ino"  the  model,  and  of  impairing  the  articulation  by  displace- 
ment of  the  teeth.  On  the  other  hand,  the  nature  of  celluloid 
is  such  that  if  it  is  exposed  to  a  temperature  of  270°,  without 
beino-  under  pressure,  the  camphor  evaporates,  and  the  material, 
besides  being  rendered  hard  and  intractable,  is  puiFed  up,  exactly 
as  a  loaf  of  bread  is  raised  by  yeast,  and  filled  with  air-cells, 
and  thus  rendered  porous. 

Celluloid  begins  to  soften  at  about  225°,  and  will  then  yield 
slightly  to  pressure,  but  this  should  be  applied  very  gently  at 


Fig.  154, 


Fig.  1.55. 


/i^iCiO^ 


A.  Reservoir,  made  of  gal- 
vanized Iron.  B.  Top  of  reser- 
voir. C.  Chimneys.  D.  Drum. 
E,  Hanging  panilion,  which 
keeps  the  radiated  heat  from 
reservoir.  F.  Principal  air 
deflectors.  H.  Supplementary 
air  deflectors.  T.  Tank  sur- 
rounding VFick  tube.  R.  Per- 
forated ring  through  which 
all  the  air  that  supplies  the  . 
stove  passes.  W.  Wick  cham. 
bar.    X.  Wick  tubes. 


first,  with  no  more  force  than  can  be  readily  exerted  with  the 
thumb  and  finger.  As  the  heat  increases,  and  the  celluloid  be- 
comes more  and  more  phistic  and  yielding,  the  pressure  should  be 
correspondingly  increased,  but  always  interruptedly,  giving  the 
material  time,  between  each  turn  of  the  screw  or  nuts,  to  escape 
from  under  the  pressure.  No  considerable  amount  of  pressure 
will  be  require<J  in  any  case  untilnearthecloseof  the  operation, 


390  MECHANICAL,   DENTISTEY. 

when  the  mould  is  completely  impacted,  and  the  excess  is  being 
forced  into  the  grooves  or  gateways  as  the  flask  comes  together. 

At  this  point,  considerable  force  will  be  necessary  to  close 
the  flask  perfectly,  and  somewhat  longer  intervals  of  time 
should  occur  between  each  turn  of  the  screw  or  nuts. 

During  the  progress  of  the  moulding,  the  flask  should  be 
withdrawn  occasionally  for  inspection.  If,  in  the  case  of  central 
pressure,  the  flask  is  found  to  be  closing  unevenly,  it  should  be 
loosened  in  the  clamp  and  readjusted  in  such  manner  as  to  cor- 
rect the  faulty  approximation.  No  difficulty  will  be  experi- 
enced in  this  respect  in  the  use  of  clamps  provided  with  screw- 
bolts,  as  pressure  may  be  applied  at  any  point,  and  the  flask  be 
made  to  close  uniformly  without  the  necessity  of  shifting  the 
latter. 

The  moment  the  flask  is  completely  closed,  the  heat  should 
be  turned  off,  and  the  piece  allowed  to  cool  gradually.  In  no 
instance  should  the  flask  be  removed  from  the  clamp  (unless 
securely  locked,  as  is  practicable  with  the  "standard"  flask),* 
until  it  is  stone  cold.  In  cases  where  the  material  is  of  extra 
thickness,  or  where  the  shape  of  the  blank  is  totally  altered, 
longer  seasoning  is  advisable,  and  the  flask  should  be  placed 
near  a  stove  or  over  a  register  (keeping  it  closed  by  a  clamp,  or 
by  an  instrument  or  j)iece  of  iron  put  through  the  holes  in  the 
standard)  for  half  a  day  or  more,  at  a  temperature  not  over 
140°.  If  these  directions  are  observed,  no  trouble  from  warp- 
ing plates  will  be  experienced. 

Moulding  in  Glycerin. — Glycerin,  as  a  medium  of  impart- 
ing heat  in  the  process  of  moulding  celluloid,  has  almost 
entirely  superseded  the  use  of  oil,  paraffin,  and  other  allied 
substances  originally  employed.  It  is  a  favorite  method  with 
many  leading  practitioners,  and  is  recommended  by  the  manu- 
facturers of  celluloid  as  superior  to  any  other.  The  long  and 
familiar  acquaintance  of  these  parties  with  the  composition, 
nature,  behavior,  and  treatment  of  the  material  they  produce, 
entitles  their  opinions  and  preferences  to  more  than  ordinary 
consideration. 

*  Manufactured  by  the  Celluloid  Company,  and  represented  in  Fig.  156. 


CELLULOID    BASE. 


391 


The  improved  glycerin  apparatus  manufactured  by  them  is 
exhibited  in  Fig.  156  ;  consisting  of  a  tank  A  for  containing 
the  glycerin  ;  a  stand  S  with  detachable  legs  L,  which  slip  into 
slots  as  shown  at  S  ;  an  alcohol  cup  shown  at  K  in  sectional 
diagram  of  steam  machine,  Fig.  158  ;  a  screw  clamp  B ;  a  flask 
C ;  and  a  thermometer  D  to  indicate  the  heat. 

Either  alcoliol  or  gas  may  be  used  with  this  machine.  When 
kerosene  is  employed,  the  manufacturers  recommend  the  use  of 
the  "  leader "  oil  stove,  which  will  be  seen  attached  to  the 
"steam"  apparatus,  Fig.  157.     When  this  stove  is  used,  the 


Fig.  156. 


lono-  lef'S  of  the  steam  machine  must  be  substituted   for  the 
shorter  ones  represented  in  Fig.  156. 

Having  placed  the  blank  in  the  flask,  put  the  latter  into  the 
screw  clamp  and  turn  down  the  screw  until  it  touciics  the  flask 
lightly;  set  the  whole  into  the  tank  and  pour  enough  glycerin 
into  the  latter  to  come  up  to  about  the  top  of  the  flask.  Apply 
heat,  aii<l  prof;eed  with  the  moulding  in  the  same  manner  as 
described  in  coiniection  with  the  "  dry  heat"  method.  The  heat 
should  not  be  permitted  to  rise  much  above  280°.    If  the  flask 


392 


MECHANICAL,  DENTISTEY. 


is  not  closed  when  that  heat  is  reached,  reduce  the  flame,  and  do 
not  hasten  the  closing.  A  little  practice  will  enable  the  operator 
to  graduate  the  pressure  exactly,  without  reference  to  the 
thermometer. 

Moulding  in  Steam. — The   best  adapted  apparatus  where 
steam  is  used  in  moulding  is  that  manufactured  by  the  Celluloid 


Fig.  15.7 


Steam  Apparatus,  with  Improved  Stand  and  Long  Legs,  adapted  to  "Leader"  Oil  Stove 

Company,  and  represented  in  Fig.  157.  A  sectional  diagram  of 
the  same  is  shown  in  Fig.  158.  It  consists  of  the  following 
parts:  (The  same  letters  represent  the  same  parts  in  both  cuts) ; 
the  base,  or  standard,  J  (now  made  with  detachable  legs,  as  in 
cut  of  glycerin  machine) ;  the  boiler  B ;  the  cover  D,  to  which 
is  attached  the  safety  valve,  H ;  the  plunger,  E,  and  alcohol 


CELLtTLdlD  BASE. 


393 


cup,  Iv  (shown  only  in  the  sectional  diagram  below) ;  the 
screw,  F,  for  closing  the  flask,  operated  by  the  handle,  L; 
the  gland  or  packing  ring,  G,  the  object  of  which  is  simply  to 
prevent  the  steam  from  leaking  around  the  screw ;  and  the 
wrench  or  spanner,  S. 


Fig.  158. 


SecUoual  Diagram. 
M  and  N,  in  the  sectional  drawing,  represent  steam  packing,  to  make  the  boiler  tight. 

The  stand  is  the  same  as  that  for  the  glycerin  machine  shown 
in  Fig.  156,  and  is  furnished  with  short  legs,  as  shown  in  that 
cut  (for  alcohol  or  gas),  or  long  legs  as  above,  as  desired.  To 
u.se  the  old  .steam  machine  with  the  "Leader  "  stove,  it  is  neces- 
sary to  order  only  the  improved  stand  with  long  legs.  The 
company  send  always  the  short  legs  unless  otiierwise  ordered. 

In  using  the  steam  machine,  care  should  be  taken  to  keep  it 


394  MECHANICAL   DEJSTTISTEY. 

in  good  order.  The  screw  should  be  well  oiled  with  only  the 
best  sperm  oil,  which  will  not  gum,  and  kept  so  that  it  can  be 
easily  turned  with  the  thumb  and  finger.  If  the  machine, 
when  received  from  the  depot,  works  hard,  the  screw  should 
be  run  out,  the  gland  unscrewed,  and  the  rubber  packing 
loosened  up,  so  that  it  will  not  bind  the  screw.  Do  not  turn 
it  down  tight  again  until  you  heat  it  up,  when,  if  it  begins  to 
leak,  it  can  easily  be  tightened.  Bear  in  mind  that  turning 
this  gland  merely  prevents  the  escape  of  steam,  and  does  not  affect 
the  p)ressure  on  the  flash. 

The  safety-valve  should  be  kept  free  from  gum,  and  if  either 
it  or  the  screw  is  fouled,  it  should  be  well  cleansed  with  kero- 
sene. This  valve,  in  the  machine  now  sold,  is  so  constructed 
that  it  blows  oif  at  about  275°,  a  temperature  that  celluloid 
will  bear  very  well ;  and  as  the  heat,  so  long  as  water  remains 
in  the  boiler,  cannot,  if  the  safety-valve  is  kept  in  order,  be 
raised  above  that  poiut,  it  is  impossible  to  hum  a  plate  in  this 
machine.  While  this  is  true,  it  is  also  true  that  too  long  an 
exposure  to  even  275°  in  steam,  tends  to  injure  the  quality  of 
the  celluloid,  and  for  this  reason  the  heat  should  be  continued 
no  longer  than  necessary,  but  should  be  at  once  reduced  by 
blowing  oif  steam  as  soon  as  the  moulding  is  completed.  The 
first  machines  were  constructed  with  the  safety-valve  much 
heavier,  and  all  in  one  piece,  and  were  adjusted  to  a  tempera- 
ture of  nearly  300°,  which  was  higher  than  necessary  or  ad- 
visable. It  is  recommended,  therefore,  that  those  having  that 
style  of  valve  should  cut  off  about  one-fourth  in  weight  from 
the  lead  weight,  which  can  be  easily  done  by  removing  a  little 
wire  which  passes  through  the  stem  and  weight.  A  modern 
valve  will  be  furnished  when  ordered.  When  moulding,  fill 
the  boiler  partly  full  of  water.  The  amount  is  not  material, 
but  there  should  always  be  enough  to  cover  the  ribs  at  the 
bottom.  Have  the  screw  well  turned  back,  until  the  plunger, 
when  placed  in  position,  will  rest  against  the  top  of  the  boiler, 
otherwise  the  flask  may  be  pressed  upon  while  screwing  down 
the  cover,  and  the  cast  injured.  Turn  down  the  cover  snugly; 
see  that  the  gland  is  turned  back,  and  the  screw  works  freely. 


CELLULOID    BASE.  395 

Many  failures  have  occurred  by  neglecting  this  simple  matter. 
If  it  works  hard,  it  is  impossible  to  tell  how  much  or  how  little 
pressure  is  being  exerted ;  there  may  be  too  much,  and  blocks 
or  cast  be  broken ;  or  too  little,  and  the  plate  made  porous. 
In  all  methods  of  working  celluloid,  the  sense  of  feeling  is  the 
best  guide  as  to  when  and  how  hard  to  turn  ;  but  in  order  to 
have  this  there  must  be  perfect  freedom  of  motion  of  the  parts. 
The  time  elapsing  before  turning  is  not  reliable,  as  it  varies 
with  the  heat  employed,  the  temperature  at  starting,  the  amount 
of  water  in  the  boiler,  the  drafts  of  air  to  which  the  flame  may 
be  subjected,  etc. 

After  placing  the  flask  in  position,  turn  down  the  screw  verij 
gently,  with  thumb  and  finger,  until  you  feel  it  touch  the  flask. 
Fill  the  cup  with  alcohol  and  light  it,  or  light  the  gas.  The 
safety-valve  is  made  in  two  parts.  The  upper  portion  may  be 
suspended  by  the  pins  in  the  lead  weight;  the  valve  will  now 
blow  ofl"  steam  (if  in  proper  order)  at  a  temperature  of  225°. 
Until  this  occurs,  no  particular  attention  is  necessary,  but  from 
that  time  the  exclusive  attention  of  the  operator  should  be 
given  to  the  moulding.  Many  failures  occur  from  the  want  of 
this,  for  the  plate  may  be  easily  injured  from  too  much  heat 
without  proper  pressure.  But  fifteen  or  twenty  minutes,  at 
the  most,  will  be  required  from  this  point,  with  proper  heat, 
and  nothing  else  should  be  attended  to. 

At  the  point  when  the  steam  escapes  from  the  valve  with  the 
upper  portion  suspended,  the  plate  will  soften,  and  the  screw 
will  be  felt  to  yield  to  light  pressure  with  thumb  and  finger. 
The  upper  weight  should  now  be  dropped  down.  Turn  the 
screw  very  carefully,  stopping  when  you  feel  the  resistance  in- 
crease ;  as  soon  as  it  yields  again,  turn  it  more,  going  slowly 
and  carefully  at  first,  but  increasing  the  pressure  somewhat  as 
the  steam  gets  u]),  which  you  will  know  by  occasionally  rais- 
ing the  valve.  It  is  just  here  that  judgment  is  required,  to 
avoid,  on  the  one  hand,  too  mu(;h  pressure  before  the  material 
is  suHificntly  softened,  which  would  result  in  fracture  of  the 
cast  or  blocks,  disarranging  the  articulation,  or  a  "  flaky " 
plate  ;  and,  on  the  other,  too  little  pressure  after  the  heat  is  up. 


39g  MECHANICAL   DENTISTRY. 

which  would  result  in  injuring  the  quality  of  the  material. 
The  pressure  should  be  followed  up  as  the  heat  rises  and  the 
sci'ew  yields,  the  object  being  to  get  the  whole  of  the  plate 
under  pressure,  in  every  part  of  the  mould,  by  the  time  the 
steam  blows  oif  quite  sharply  and  steadily  on  raising  the  safety- 
valve.  After  this,  the  pressure  should  be  increased,  but  time 
should  always  be  given  between  the  turns  for  the  slowly  flow- 
ing celluloid  to  escape  from  under  the  pressure.  Toward  the 
close  of  the  process,  the  pressure  should  be  considerable ;  in 
in  fact,  about  all  that  can  be  applied  with  the  machine,  and 
should  be  continued  as  long  as  the  screw  can  be  turned.  If 
the  operation  has  been  properly  timed,  the  steam  will  blow  off 
at  the  safety-valve  at  about  the  time  the  moulding  is  completed, 
and  the  alcohol  in  the  cup  is  consumed.  If  it  should  blow  off" 
before  that,  no  harm  would  be  done,  as  the  heat  cannot  become 
too  great  if  the  safety-valve  is  kept  in  proper  condition.  These 
remarks  apply  to  the  use  of  alcohol  in  the  cup  furnished  with 
the  machine.  If  any  other  heat  is  used,  the  flame  should  be 
sufficient  to  complete  the  process  within  thirty  to  forty  minutes. 
If  more  than  this  time  is  consumed  in  the  moulding,  the 
quality  of  the  plate  is  injured. 

Do  not  allow  the  water  to  be  all  converted  into  steam,  as  the 
steam  would  then  become  superheated,  and  a  dangerous  condi- 
tion ensue  or  the  plate  be  ruined,  while  the  safety-valve  would 
not  indicate  it.  Always  have  plenty  of  water  in  the  boiler, 
and  if  steam  should  cease  to  issue  on  raising  the  valve,  the 
heat  should  be  at  once  withdrawn. 

Repairing. — This  is  very  easily  and  satisfactorily  accom- 
plished. Cut  away  the  plate,  and  fit  in  the  new  teeth  or 
block.  Dovetails  or  holes  may  be  made,  but  they  are  unnec- 
essary. Always,  if  possible,  before  flasking,  fit  a  new  piece, 
much  larger  than  the  portion  cut  away,  to  the  plate  as  closely 
as  possible,  and  let  it  come  as  close  as  possible  to  the  added 
te»th ;  then,  having  the  surfaces  clean,  cement  it  fast  with 
spirits  of  camphor,  or  a  solution  of  celluloid  and  camphor. 
Allow  it  to  dry,  after  which  the  new  teeth  should  be  waxed 
into  place.     Invest  the  piece  in  the  flask,  covering  the  whole 


CELLULOID    BASE. 


397 


plate  and  teeth  in  the  plaster,  except  the  added  piece,  Avhich 
should  be  left  at  the  bottom  of  a  well  or  depression  in  the 
plaster. 


The  above  cut  will  show  the  manner  of  repairing,  and  make 
it  as  plain  as  can  be  done  in  print.  No.  1  shows  the  first  step 
in  the  process,  the  plate  being  cut  away  and  the  new  piece 
(shown  at  "a")  fitted  and  cemented  in  place.  After  drying  a 
short  time  (allowing  it  to  stand  a  few  hours  or  over  night  if 
convenient),  fit  the  new  block  to  its  place,  leaving  as  little 
space  as  possible  between  the  plate  and  block ;  this  space  is  to 
be  waxed  up  to  keep  out  plaster  when  investing.  Fig.  1 59 
shows  the  piece  invested,  the  whole  plate  and  teeth,  except  the 
new  piece  "  a,"  being  covered  deep  in  the  plaster,  which  is 
trimmed  as  shown.  The  upper  part  of  the  flask  is  now  put  in 
place,  and  filled  in  the  usual  manner.  On  opening  the  flask 
Vjoil  out  the  wax.  Then  lay  another  piece  of  celluloid,  or  a 
ball  of  tin  foil,  or  moistened  blotting-pad — in  fact  anything 
that  will  produce  pressure,  upon  the  piece  "o,"  and  heat  up 
and  press  as  usual.  In  this  way  the  new  piece  becomes  a  par^ 
of  the  plate  })y  the  cementing  process,  before  the  pressing  is 
done,  and  will  not  scale  or  separate.  If  neatly  done,  the  line 
of  junction  will  be  scarcely  observable.  The  sharp  edge  of  the 
plaster  at  the  bottom  of  the  well  or  depression  should  be 
trimmed  out  and  well  rounded,  as  otherwise  these  edges  are 


398  MECHANICAL   DENTTSTEY. 

liable  to  fracture  and  get  into  the  plate.  If  the  new  block  or 
tooth  is  separated  from  the  plate,  so  that  it  has  no  support,  and 
is  liable  to  be  pushed  down,  it  should  be  supported  by  crowd- 
ing a  small,  bit  of  celluloid  under  it  before  beginning.  The 
new  piece  may  be  placed  in  position  after  opening  the  flask,  a 
few  drops  of  spirits  of  camphor  added,  and  the  case  pressed  as 
before ;  but  union  by  this  means  is  not  nearly  as  certain.  There 
is  no  certainty  about  uniting  pieces  in  the  machine.  It  may  be 
done,  or  it  may  not.  But  by  cementing  well-fitting  or  freshly 
filed  surfaces  together  outside  the  flask,  perfect  union  may 
always  be  had,  and  pieces  added  wherever  desired.  In  invest- 
ing, the  plate  should  always  be  placed  in  a  position  the  reverse 
of  that  indicated  by  the  cut  on  page  382,  in  order  that  a  direct 
downward  and  not  a  side  pressure  may  be  had.  Care  should 
be  taken  to  avoid  air-bubbles  in  the  plaster,  and  to  pour  it 
smoothly. 

If  the  plate  is  of  sufficient  thickness,  the  repair  may  be  very 
nicely  made  without  adding  any  new  material.  Fit  the  new 
block  without  cutting  away  more  of  the  plate  than  absolutely 
necessary.  Invest  the  plate,  leaving  the  tongue  side  exposed, 
but  covering  the  teeth ;  on  opening  the  flask,  lay  over  the  ex- 
posed plate  one  or  more  thicknesses  of  wet  thick  brown  paper, 
blotting-pad,  or  unvulcanized  rubber,  fitting  closely  to  the 
teeth  and  having  it  thickest  in  the  centre,  and  press  as  usual. 
By  this  means  the  plate  will  be  spread  up  to  the  new  teeth, 
which  will  be  firmly  united.  Loose  teeth,  if  any,  on  the  plate 
may  be  tightened  by  the  same  means,  having  been  waxed  in 
place,  and  the  wax  afterwards  thoroughly  boiled  out.  Some 
dentists  attempt  to  mend  in  this  way,  without  using  anything 
to  produce  pressure,  depending  upon  the  swelling  of  the  plate 
to  fill  the  vacancy.  This  would  be  certain  to  injure  the  density 
of  the  plate. 

To  remove  teeth,  heat  the  plate  in  boiling  water  or  glyc- 
erin, when  they  will  easily  come  oif. 

Rubber  plates  may  be  very  nicely  repaired  with  celluloid, 
but  as  there  is  no  union,  dovetailing  or  drilling  holes  is 
necessary. 


CELLULOID    BASE.  399 

Finishing. — This  is  accomplished  in  one-half  the  time  nec- 
essary with  rubber.  Use  files,  sandpaper,  and  scrapers,  but 
do  not  use  too  coarse  materials.  Polish  with  pumicestone,  and 
finish  with  a  soft  brush  at  high  speed,  and  whiting  or  Vienna 
lime.  Dr.  H.  D.  Knight,  of  Lancaster,  Pa.,  recommends  a 
polish  obtained  by  rubbing  with  an  old  cloth  wet  with  cam- 
phor. This  may  be  valuable  between  teeth,  and  in  places  in- 
accessible with  the  brush-wheel.  In  finishing,  care  should  be 
taken  not  to  heat  the  plate  by  friction,  as  by  so  doing  the  sur- 
face may  be  injured,  or  the  plate  sprung  out  of  shape. 


400  MECHANICAL  DENTISTEY. 


CHAPTER  Xyi. 

Attaching  Porcelain  Teeth  to  a  Metallic  Base 
WITH  Rubber  or  Celluloid. 

The  following  method  of  attaching  porcelain  teeth  to  a 
metallic  plate  by  means  of  rubber  or  celluloid,  though  but 
little  practiced  heretofore,  is  attracting  more  attention  than  for- 
merly, and  is  eminently  deserving  of  more  favorable  considera- 
tion and  general  adoption,  by  reason  of  its  conspicuous  and 
acknowledged  merits,  than  it  has  ever  yet  received.  The 
credit  of  its  first  introduction  to  the  notice  of  the  profession  is 
due  to  Dr.  P.  G.  C.  Hunt,  of  Indianapolis,  Ind.,  who  prac- 
ticed the  method  as  early  as  1859,  and  whose  published  de- 
scriptions of  the  manner  of  preparing  the  plate  base,  substan- 
tially the  same  as  that  for  which  Mr.  S.  D.  Engle,  of  Hazle- 
ton,  Pa.,  obtained  letters  patent  some  years  later,  were  given 
in  the  first  edition  of  this  work. 

In  commenting  on  this  method.  Professor  Charles  J.  Essig 
very  justly  remarks  that,  by  the  means  here  indicated,  we  are 
"  able  to  produce  an  artificial  denture  embracing  all  that  is 
good  in  metallic  and  vulcanite  work,  at  the  same  time  avoid- 
ing the  great  defects  of  each." 

That  it  possesses  marked  advantages  over  the  method  of 
attaching  teeth  to  a  metallic  plate  base  by  soldering  is  unques- 
tionable. The  warping  and  consequent  change  in  the  form  of 
the  plate  incident  to  soldering,  so  inseparable  from  the  older 
method  of  attachment  by  means  of  stays  or  backings,  is  wholly 
avoided ;  the  strain  upon  the  platina  pins  is  greatly  lessened 
by  reason  of  the  perfectly  adapted  rubber  or  celluloid  socket 
in  which  each  tooth  or  block  securely  rests ;  the  liability  to 
fracture  of  the  teeth  from  concussion  or  violence  is  materially 
diminished  on  account  of  the  pliable  nature  of  the  attaching 


METALLIC   BASE   WITH    RUBBER   ATTACHMENT.         401 

material  used  ;  a  nearer  approximation  to  the  natural  form  of 
the  ridge  or  guiu  on  the  lingual  side  of  the  plate  is  secured ; 
the  rubber  or  celluloid,  penetrating  all  the  joints  and  openings 
between  and  underneath  the  teeth,  renders  the  piece  wholly  im- 
jjervious  to  the  oral  secretions,  making  it,  in  point  of  cleanli- 
ness and  purity,  equal  to  continuous  gum  work ;  the  facility 
with  which  injury  to  the  teeth  may  be  repaired ;  the  practica- 
bility of  remodelling  the  piece  without  impairment  of  the 
teeth  or  plate ;  its  susceptibility  of  receiving  a  final  finish  ex- 
celled by  no  other  method  in  point  of  artistic  beauty ; — these 
are  among  the  qualities  which  commend  this  method  of  sub- 
stitution as  one  of  peculiar  merit  and  excellence. 

In  mounting  teeth  by  this  method,  preference  should  be 
given  to  either  gold  or  platinum  as  a  base.  When  silver  is 
used,  the  plate  should  be  made  from  refined  silver  alloyed 
with  platinum,  with  the  additional  precaution  of  interposing  a 
layer  of  tin  foil  between  the  rubber  and  plate,  an  expedient 
not  necessary  when  celluloid  is  employed.  Aluminum  has  a 
limited  adaptability  to  this  mode  of  substitution,  but  requires 
special  treatment  in  its  preparation  for  the  purpose,  a  descrip- 
tion of  which  will  be  given  in  connection  with  the  manner  of 
preparing  the  plate. 

The  manipulative  details  concerned  in  the  construction  of 
an  artificial  denture  by  the  method  under  consideration  are 
thus  described  by  Dr.  Hunt : 

"  Take  the  impression,  make  metallic  dies,  and  form  the 
plate  as  for  work  in  the  ordinary  way.  After  fitting  the  plate 
in  the  mouth,  get  the  articulation,  the  fulness  and  length  of  the 
teeth,  remove  the  wax  and  plate  from  the  mouth  and  make  the 
plaster  articulation.  If  a  full  set,  after  separating  the  articula- 
tion, and  before  removing  the  wax  from  the  plate,  take  a  small 
light  pair  of  dividers,  set  tliem  say  one  inch  apart,  and  with  one 
point  following  the  margin  of  the  wax  representing  the  cutting 
edge  of  the  teeth,  and  tlie  other  point  marking  permanently 
the  plaster,  you  liave  always  in  the  dividers  so  set  a  gauge 
for  the  length  of  any  particular  tooth.  A  convenient  substi- 
tute for  the  dividers  may  be  formed  from    a   i)iece  of  wire 

26 


402 


MECHANICAL   DENTISTEY. 


of  convenient  length,  one-half  the  diameter  of  a  common  ex- 
cavator, by  suitably  twisting  its  middle  for  a  handle,  and  its 
ends  being  sharpened,  and  pointing  in  the  same  direction,  one 
or  one  and  a  half  inches  apart. 

"  Thus  far  we  proceed  as  we  do  for  ordinary  gold  work.  We 
will  now  suppose  the  teeth  ground  and  jointed,  leaving  as  much 
space  between  the  teeth  and  plate  as  the  plate  will  admit  of. 
We  next  mark  with  a  sharp-pointed  instrument  on  the  labial 
surface  of  the  plate  each  point  where  it  is  necessary  to  place  a 
loop  for  purposes  hereinafter  described.  Then  apply  wax  to 
the  external  or  labial  parts  of  the  teeth  and  plate  in  any  man- 
ner sufficient  to  retain  the  teeth  in  position,  remove  the  wax 


from  the  lingual  parts  of  the  teeth  and  plate,  and  mark  the 
position  on  the  metal  where  it  is  desirable  to  insert  loops,  re- 
move the  teeth  and  wax,  and  with  a  small  bow-drill  make 
holes  through  the  plate  at  the  several  points  previously  deter- 
mined on  for  the  attachments,  about  the  size  of  the«ordinary 
plate  punch-hole,  take  a  wire,  or  ordinary  gold  plate,  cut  in 
strips,  say  from  a  half  to  one  line  in  width,  being  governed  by 
the  amount  of  room  there  is  under  the  base  of  the  teeth, 
and  with  small,  round-nosed  pliers,  bend  the  strip  around, 
grasp  both  ends  with  square-nosed  pliers,  draw  the  round-nosed 
pliers  from  the  loop,  still  grasping  the  square-nosed  pliers 


METALLIC   BASE   WITH    RUBBER   ATTACHMENT.        403 

with  the  left  hand,  and  with  a  hammer  strike  the  top  of  the 
loop  a  sufficient  blow  to  keep  the  ends  from  springing  apart. 
Cut  off  the  ends,  and  dress  down  to  fit  the  holes  in  the  plate, 
after  which  solder  on  charcoal  or  other  suitable  substance 
without  investment." 

By  reference  to  Fig.  160,  wliich  illustrates  ]\Ir.  Engle's 
method  of  providing  attachment  for  the  rubber  to  the  plate  by 
means  of  bent  or  hooked  wires  soldered  to  the  base,  the  sub- 
stantial identity  of  Dr.  Hunt's  mode  of  forming  loops  for  the 
same  purpose  will  be  apparent. 

With  this  digression  we  return  to  Dr.  Hunt's  instructions  : 

"  Pickle,  dress,  and  polish  that  portion  of  the  plate  to  be 
exposed  to  view.  Bend  and  flatten  the  pins,  arrange  the  teeth 
according  to  the  articulation,  waxing  so  as  to  cover  up  the 
loops  if  practicable ;  the  loops  should  be  placed  as  near  the 
base  of  the  teeth  as  possible,  the  rubber  forming  when  finished 
a  part  of  that  general  concave  shape  which  is  desirable  in  upper 
dentures,  and  which  it  is  not  possible  to  obtain  with  the  ordi- 
nary soldered  work.  Then  with  silicate  of  soda  paint  the  joints, 
to  keep  the  rubber  from  forcing  in  where  it  would  show  after 
vulcanizing.  Flask,  vulcanize,  and  finish  up  as  usual.  The 
advantages  of  this  style  of  work  are  obvious.  With  this  you 
have  work  as  cleanly  as  the  continuous  gum,  decidedly  more 
so  than  the  very  best  single  gum  or  block-work  soldered  in  the 
usual  way ;  again  it  is  very  much  stronger,  less  liable  to  break- 
age, both  in  and  out  of  the  mouth,  as  the  rubber  gives  a  jyer- 
fect  base  and  support  for  the  teeth  to  set  upon.  By  this  method 
there  is  no  springing  of  plates.  As  your  plate  fits  the  mouth 
when  the  articulation  was  taken,  so  will  be  the  fit  when  the 
case  is  completed. 

"  On  the  labial  edge  of  the  upper  plate  the  rubber  may  be 
allowed  to  project  beyond  the  edge,  if  desirable,  and  it  will  be 
found  in  many  cases  exceedingly  satisfactory  to  do  so,  and 
allow  the  rui)ber  to  be  of  considerable  thickness  near  the  alas 
of  the  nose,  where  the  loss  of  the  cuspidati  may  leave  a  want 
of  support  to  the  soft  parts  adjacent,  and  which  in  this  manner 
can   be    readily  corrected.       If  the  rubber  extends   upwards 


404  MECHANICAL,   DENTISTEY. 

SO  far  as  to  irritate  the  muscular  structure,  a  few  minutes  will 
be  sufficient  to  make  the  necessary  alterations.  In  all  such  cases 
where  we  have  control  of  our  patients,  we  place  the  denture 
in  the  mouth  before  finally  polishing,  so  as  to  determine  as 
accurately  as  possible  the  limit  to  which  extension  upward  may 
be  carried. 

"  The  neatest  work  on  this  principle  is  made  by  carving 
blocks,  giving  to  the  lingual  surface  that  regular  concave  form 
which  is  desirable.  In  this  no  platinum  pins  or  loops  are 
necessary,  but  that  half  of  the  matrix  on  which  the  blocks  are 
carved,  large  metallic  pins  are  so  arranged  as  to  be  hid.  from 
view  in  the  tooth  body.  DiiFerent-sized  pins  maybe  used,  as  large 
as  the  nature  of  the  case  will  admit.  In  short,  we  make  the  holes 
in  the  block  similar  to  those  in  pivot  teeth,  where  there  is  not 
sufficient  room  in  the  block  above  the  tooth  (or  below  if  an 
under)  to  allow  the  pins  to  run  into  the  body  of  the  teeth. 
After  burning,  grinding,  and  fitting,  get  the  position  of  the 
holes  in  the  blocks  relative  to  the  plate,  and  drill  through  the 
plate  as  before,  and  instead  of  loops,  solder  gold  wire  of  suit- 
able size  and  length,  say  a  very  little  shorter  than  the  depth  of 
the  hole  in  the  blocks,  and  two-thirds  the  diameter  thereof;  the 
wire  should  have  a  screw-thread  cut  on  it,  or  that  which  is 
just  as  good,  and  more  expeditious,  barb  or  cut  with  a  sharp 
knife.  At  this  point  of  the  manipulation,  if  it  is  desired  that 
the  rubber  should  extend  beyond  the  labial  or  buccal  edge  of 
the  metallic  j)late,  place  as  many  loops  at  different  points  as 
are  sufficient  to  retain  it  with  firmness,  after  which  polish  the 
plate,  wax,  and  proceed  as  before  described.  If  you  desire  no 
rubber  beyond  the  blocks,  the  roughness  of  the  holes  in  the 
same,  and  the  barbed  points  on  the  gold  wire  when  properly 
packed  and  vulcanized,  will  give  ample  strength  and  firmness 
to  the  case,  and  if  care  has  been  used  in  the  entire  manipula- 
tion, you  will  have,  when  finished,  but  a  thin  line  of  rubber 
exposed  to  view. 

"  In  partial  cases,  if  of  gold  base,  solder  on  loops,  as  before, 
for  the  retention  of  the  teeth,  and  if  there  are  to  be  any  clasps, 
make  them  of  rubber,  uniting  them,  as  the  teeth,  with  loops. 


MKTALLIC   BASE   WITH    RUBBER    ATTACHMENT.        405 

If  the  ordinary  plate  teeth  are  used,  it  is  frequently  necessary 
to  back  them,  to  give  better  retain ing-points  for  the  rubber. 
If  blocks  are  to  be  burned,  insert  loops  of  platinum  plate  in 
the  shape  of  the  letter  U  in  place  of  the  platinum  wire  pins. 
In  consequence  of  the  affinity  of  the  sulphur  in  the  vulcanite 
for  silver,  plates  of  that  metal  should  not  be  used." 

The  following  method  of  preparing  aluminum  plates  for  the 
attachment  of  the  rubber,  was  communicated  to  the  author  by 
Dr.  J.  W.  Hollingsworth,  of  Greencastle,  Indiana,  an  intelli- 
gent practitioner,  who  has  had  long  and  extended  practical  ex- 
perience in  the  various  modes  of  working  this  metal  for  dental 
purposes,  and  who  says  of  the  following  mode  of  procedure, 
that  "  it  is  the  most  practicable  and  the  most  easily  manipu- 
lated method  that  I  have  yet  seen." 

The  following  is  the  manner  of  preparing  the  plate  as  de- 
scribed by  Dr.  Hollingsworth :  "  Perforate  the  ridge  of  the 
plate  at  proper  points  and  intervals  ;  then  pass  through  these 
perforations,  from  the  inner  surface  of  the  plate,  headed  pins 
made  of  aluminum,  which,  after  replacing  the  plate  with  the 
pins  back  upon  the  die,  we  shrink  down  to  permanency  with  a 
hollow  punch.  The  punch  must  be  made  with  the  hole  not 
quite  equal  in  depth  to  the  length  of  the  extruding  portion  of 
the  pins,  and  slightly  bell-mouthed.  This  riveting  process 
forms  seriate  studs  or  pins,  which  may  be  bent  or  flattened 
with  pliers  in  any  way  to  suit  the  requirements  of  the  case." 

When  celluloid  is  used  for  purposes  of  attachment  in  the 
case  of  upper  entire  dentures,  the  palatal  portion  of  the  blank 
should  be  cut  or  sawed  away,  leaving  only  the  ridge  portion  to 
be  used,  and  this  should  be  trimmed,  if  necessary,  so  as  to  have 
but  little  excess  of  material.  The  ordinary  full  blank  may  be 
used  for  lower  ca.ses,  observing  the  same  precautions  in  regard 
to  quantity  of  material.  When  the  blank  is  thus  prepared, 
the  subsequent  manipulations  are  the  same  as  those  described 
in  connection  with  the  celluloid  base. 

It  may  be  observed  that,  when  rubber  or  celluloid  is  .used, 
it  is  l>etter  to  dispense  with  the  plaster  model  in  forming  the 
mould  or  matrix,  and  proceed  as  follows :  When  the  teeth  are 


406  MECHANICAL,   DENTISTRY. 

arranged,  and  the  required  contour  and  fulness  given  to  the 
wax  drafts,  fill  the  lower  section  of  the  flask  with  plaster,  and 
(having  also  filled  the  plate  with  the  same),  imbed  the  plate 
in  it,  making  the  dividing  line  on  the  external  rim  of  wax. 
When  the  plaster  has  hardened,  and  the  other  section  formed, 
and  the  two  afterwards  separated,  the  metallic  plate  will  remain 
in  the  lower  section,  and  the  teeth  in  the  upper. 

When  using  celluloid,  plain  teeth  may  be  advantageously- 
employed,  the  former  representing  the  gum  ;  this  gives  perfect 
freedom  in  the  arrangement  of  each  separate  tooth  in  the  den- 
ture, an  optional  disposition  the  importance  of  which  cannot 
be  over-estimated. 


GOLD    ALLOY   CAST    BASE.  407 


CHAPTER  XYII. 
Gold  Alloy  Cast  Base. 

The  compound  of  gold,  silver,  and  tin,  in  varied  propor- 
tions, in  connection  with  specific  and  original  methods  of  cast- 
ing dental  plates,  recently  devised  and  patented  by  Dr.  George 
F.  Reese,  of  Brooklyn,  N.  Y.,  is  attracting  attention  as  a  pos- 
sible substitute  for  the  plastic  materials  so  commonly  employed 
as  a  base  for  artificial  dentures. 

The  properties  and  capabilities  attributed  to  this  alloy,  and 
which  are  deemed  essential  in  a  base,  having  been  practically 
tested  by  many  representative  and  responsible  practititioners 
who  have  unreservedly  indorsed  its  claims  upon  the  confi- 
dence of  the  profession,  the  author  feels  warranted  in  substi- 
tuting Dr.  Reese's  materials  and  processes  for  the  older  alloys, 
appliances,  and  modes  of  manipulation  described  in  former 
editions  under  the  head  of  "  Cheoplastic  Method  of  Mounting 
Artificial  Teeth,"  and  which,  for  many  years  past,  have  been 
wholly  abandoned  except  in  the  case  of  lower  dentures  where 
extreme  and  exceptional  absorption  of  the  alveolar  processes 
make  greatly  increased  weight  necessary  to  provide  against 
mobility  and  displacement  of  the  substitute. 

After  premising  that  the  methods  in  common  use  for  cast- 
ing alloys  were  not  applicable  to  one  having  the  molecular 
properties  of  Reese's  compound,  the  inventor  says  he  was  led, 
after  multiplied  experiments,  to  adopt  the  plan  of  which  the 
following  is  a  description  : 

Th(;  impression  is  taken  with  plaster,  to  which  salt  or  sul- 
phate of  potassa  has  been  added,  and  the  model  obtained  from 
this  with  pure  j)laster.  Upon  this  the  teeth  are  arranged.  For 
the  trial  plate,  gutta-percha,  paraffin,  and  wax,  or  modelling 
compound,  may  be  used.     When  satisfaction  in  the  occlusion 


408 


MECHA]SriCAL   DENTISTEY. 


is  attained,  then  the  case  is  returned  to  the  model,  and  the 
waxing  around  the  labial  and  buccal  borders  of  the  teeth  com- 
pleted. That  portion  of  the  trial  plate  which  covers  the  pal- 
atine surface  is  now  removed,  so  that  the  pins  of  the  teeth  will 
be  nearly  exposed  ;  allowing  the  wax  which  is  under  the  gums 
to  remain.  That  the  plate,  after  casting,  shall  not  be  too 
cumbrous,  the  trial  plate,  which  has  been  removed,  must  be  sub- 
stituted with  two  thicknesses  of  French  flower  wax,  cut  care- 
fully to  the  model,  and  pressed  down  closely  with  the  finger 


in  a  manner  that  no  wrinkles  will  appear  to  mar  the  beauty 
of  the  work. 

Fig,  161  represents  a  case  thus  prepared.  The  dotted  lines 
show  the  borders  of  the  thin  wax.  B,  A,  and  C,  represent  nip- 
ples of  solid  wax,  fixed  to  the  posterior  border  and  to  the 
tuberosities ;  A  and  C  being  the  places  of  exit  for  the  molten 
metal  into  the  waste  pockets,  and  B  the  place  of  entrance  of 
the  metal  from  the  pouring-gaine. 

The  case  is  now  transferred  to  the  small  brass  flask,  r. 
Fig.  162,  the  sections  of  which  having  been  well  oiled,  upon 
the  inner  surface,  to  facilitate  their  removal  from  the  invest- 
ment.    Either  section  is  then  placed  upon  a  plate  of  glass  and 


GOLD    ALLOY    CAST    BASE. 


409 


plaster  poured  into  it  until  half  filled.  The  model,  as  pre- 
pared, after  being  well  saturated  with  water,  is  imbedded  in 
this  single  section,  allowing  the  teeth  and  gums  to  remain  un- 
covered. Set  on  the  counter-part  of  the  flask  and  add  more 
plaster  along  the  posterior  border  until  the  nipples  are  reached 
or  slightly  covered.  After  this  has  set,  the  upper  section  may 
be  removed  and  the  surface  of  the  plaster  covered  with  a  thin 
solution  of  shellac^  Elliott's  parting  fluid  or  vaselin.     Return 

Fig.  162. 


Case  ready  for  the  completion  of  Investment. 

the  section  and  complete  the  investment.     Fig.  162  shows  the 
case  thus  made  ready. 

After  a  proper  time  place  the  flask  in  hot  water  that  it  may 
be  separated  without  injury.  When  separated,  wash  away  all 
the  wax,  and,  by  means  of  gentle  tapping,  remove  the  flask  rings 
from  the  investment  and  set  them  aside.  The  depressions 
formed  i>y  the  nipples  may  now  be  extended  tiirough  the  plas- 
ter to  the  external  edge ;  or,  if  the  circumstances  of  the  case 


410 


MECHANICAL   DENTISTRY. 


make  this  impossible,  the  channels  may  be  made  at  the  line  of 
division  between  the  two  sections,  as  shown  by  the  dotted  lines 
m  figures  163  and  164.  Externally,  the  channels,  D,  E,  F, 
Fig.  164,  should  be  neatly  countersunk  and  varnished  with 


Fig.  163. 


shellac  to  receive  the  pockets.  The  latter  are  made  of  the 
French  wax  by  warming  and  wrapping  the  same  around  a 
cone-shaped  stick,  and  the  base  and  apex  of  the  cone  neatly 
trimmed  of  all  inequalities.  These  pockets  should  be  about 
one  and  a  half  inches  long,  and  about  half  an  inch  diameter  at 


GOLD   ALLOY   CAST   BASE. 


411 


the  base,  and  an  eighth  of  an  inch  at  the  apex.  The  pouring- 
gaine  is  made  in  the  same  manner,  but  should  be  smaller  in 
diameter  at  the  base,  and  about  two  inches  long.  After  re- 
moving these  wax  covers  from  the  moulding-sticks,  the  larger 
ends  of  each  should  receive  a  thin  wax  cover  secured  to  its 
place,  and  made  water-tight,  by  flowing  hot  wax  along  the 
line  of  junction,  after  the  manner  of  soldering.  Trim  the 
covers,  then  place  the  smallest  ends  of  the  large  cones  in  the 
counter-sunk  channels  at  the  tuberosities  and  the  small  cone 
in  the  middle  hole,  and  secure  them  with  melted  wax.  Fig. 
163,  d',  e',/',  shows  the  pockets  thus  attached. 


Upper  or  counter  section  corresponding  to  Fig.  163.    D,  E,  F,  channels  for 
entrance  and  exit  of  metal. 

Should  the  channels  have  been  made  through  the  solid 
plaster  of  the  lower  section,  as  in  Fig.  163,  then  the  upper 
section,  P'ig.  164,  need  not  be  joined  to  it  until  after  the  pockets 
are  secured  to  their  places.  Should,  however,  tiie  channels 
have  been  made  uj)on  the  line  of  division,  then  the  sections 
must  l>e  joined  before  the  pockets  can  be  attached. 

The  case  is  now  ready  for  a  second  investment,  which  is 


412 


MECHANICAL  DENTISTRY. 


done  in  a  flask  sufficiently  large  to  embrace  the  case  as  it  now 
presents.  Fig.  165  represents  the  construction  of  the  large  flask. 
One  section  of  the  same  is  placed  upon  glass  and  about  half 
filled  with  plaster.  The  case,  having  been  well  soaked  with 
cold  water,  is  laid  carefully  upon  the  plaster,  allowing  the  long 
cone  to  rest  in  the  notch  at  the  heel  of  the  flask,  and  the  waste 
pockets  to  become  imbedded  in  the  plaster.  Immediately  put 
the  other  section  of  the  flask  in  place  and  complete  the  invest- 


FiG.  165. 


ment  by  filling  with  plaster  the  uppermost  section  to  fulness. 
Of  course  there  will  be  no  division  of  the  sections  as  was  the 
case  in  the  former  flashing.  After  solidification,  the  pouring- 
gaine  must  be  neatly  trimmed  and  countersunk,  and  great 
care  must  be  exercised  that  no  dirt  be  allowed  to  enter  the 
channel. 

The  wax,  which  is  imbedded  in  the  plaster,  and  which  forms 
the  waste  pockets,  will  be  entirely  absorbed,  and  no  trace  of  it 
will  be  seen  upon  opening  the  flask. 


GOLD   ALLOY   CAST   BASE. 


413 


All  is  now  ready  for  drying.  This  is  done  in  an  oven 
specially  prepared  for  the  purpose,  but  it  may  be  accomplished 
in  any  way  to  be  chosen  by  the  manipulator.  'An  ice-cold 
mouth-mirror  placed  over  the  opening  of  the  pouring-gaine 
will  detect  the  slightest  moisture  which  may  remain,  and  until 
this  is  entirely  dispelled,  the  casting  should  not  be  attempted. 

There  are  several  grades  of  the  gold  alloy,  as  compounded 
by  Dr.  Reese,  which  require  a  heat  registering  from  600°  to 


Fig.  166. 


-     S 


700°  Fah.  to  melt,  but  a  higher  temperature  than  this  must  be 
attaine<^l  before  pouring,  in  order  to  secure  a  satisfactory  flow. 
At  900°  rapid  oxidation  takes  place.  This,  of  course,  should 
be  avoided.  The  alhjy  may  be  melted  in  an  ordinary  iron 
ladle  or  crucible  over  a  gas  or  other  flame,  and  should  be 
poured  while  the  mould  is  hot. 

After  the  lapse  of  an  hour  or  two,  or  until  tiic  cast  is  suffi- 
ciently cooled  to  insure  the  integrity  of  the  teeth,  it  may  be 


414  MECHANICAl.  DENTISTRY. 

placed   in  warm  water,  when  the  investment  can  be  easily 
removed. 

Fig.  166  represents  the  cast  after  removal.  The  surplus 
metal  may  be  separated,  along  the  dotted  line  S,  with  a  ribbon 
saw,  after  which  the  denture  is  ready  for  the  pumice-wheel  and 
brush.     Fig.  167  represents  the  finished  case. 

Fig.  167, 


Repairing. — The  process  of  repairing  broken  plates  is,  in 
principle,  the  same  as  above.  A  flask,  specially  constructed 
by  the  inventor,  is  used  for  this  purpose,  whereby  a  single  in- 
vestment suffices.  Suppose,  for  example,  a  plate  is  broken, 
from  the  labial  to  the  posterior  border,  along  the  median 
line;  the  broken  edges  are  scraped  clean,  and  a  separation 
made  of  about  an  eighth  of  an  inch.  The  parts  are  then  ad- 
justed upon  the  model,  and  the  space  between  the  approximate 
edges  filled  with  wax.  At  each  extremity  of  the  fissure  a  pen- 
cil of  wax,  an  eighth  of  an  inch  in  diameter,  and  one  and 
a  half  inches  long,  is  securely  attached,  perpendicularly,  to  the 
palatine  surface,  and  the  whole  surrounded  with  plaster  to  the 
depth  of  one  inch.  Thus  will  be  constituted  two  sections, 
which  are  separated,  and  the  wax  washed  out.  The  external 
ends  of  the  channels,  formed  by  the  pencils,  are  then  countersunk, 
and  into  each  is  inserted  a  wax  cone,  the  one  forming  a  pour- 
ing-gaine,  and  the  other  a  waste-pocket.  The  latter  should  be 
entirely  covered  by  the  plaster.     The  whole  is  now  invested  in 


GOLD   ALLOY   CAST   BASE.  415 

the  repair  flask,  and  subsequently  submitted  to  the  process  of 
drying. 

Dr.  W.  S,  Elliott,  of  New  York,  has  taken  advantage  of 
the  method  above  described,  to  overcome  the  difficulties  attend- 
ing the  construction  of  continuous-gum  work. 

To  maintain  a  perfect  adaptation  of  a  swaged  plate  seems 
often  impossible,  in  consequenc^e  of  the  springing  of  the  plate 
in  the  furnace.  To  avoid  this  difficulty,  the  following  plan  is 
suggested :  The  plaster  model  is  first  covered  with  two  thick- 
nesses of  French  flower  wax,  carefully  adjusted.  From  this  a 
metallic  die  and  counter-die  are  made,  and  a  very  thin  (No.  32) 
platina  plate  is  swaged  to  fit  the  waxed  model.  The  labial 
border  need  not  be  returned  as  in  ordinary  cases.  Upon  this 
the  teeth  are  arranged,  and  the  case  is  transferred  to  the  fur- 
nace for  biscuiting  and  enamelling.  After  proper  annealing,  it 
is  ref)laced  upon  the  model  and  waxed  up,  on  the  labial  and 
buccal  borders,  over  the  edge  of  the  j)late ;  then  flashed,  the 
wax  removed,  and  the  metal  cast  upon  it  in  the  manner  hereto- 
fore described. 

Danger  of  checking  the  enamel  is  associated  with  the  pro- 
cess ;  but  success  has  attended  the  effort,  and  it  is  hoped  that 
present  experiments  will  insure  perfect  and  uniform  results. 


416  MECHANICAL   DENTISTEY. 


CHAPTER  Xyill. 

Defects  of  the  Palatal  Oegans,  and  their  Treat- 
ment BY  Artificial  Means. 

•  DR.  KINGSLEY's  artificial  VELUM   AND  PALATE.* 

Palatine  Defects. — Defects  of  the  palatine  organs  may  be 
divided  into  two  classes,  viz.,  accidental  and  congenital.  The 
first  includes  all  loss  of  substance  in  either  hard  or  soft  palate 
by  disease  or  otherwise.  Such  defects  are  not  uniform  in 
locality  or  extent,  being  sometimes  but  a  simple  perforation  of 
the  palate,  and  at  others  involving  the  destruction  of  the  entire 
soft  palate,  a  considerable  portion  of  the  hard  palate,  the  vomer 
and  turbinated  bones,  and  the  loss  of  the  teeth. 

The  second  class  includes  all  malformations,  from  the  simple 
division  of  the  uvula,  to  an  opening  through  the  velum,  pala- 
tine, and  maxillary  bones,  and  a  division  of  the  upper  lip, 
thus  uniting  throughout  their  entire  extent  the  nasal  passages 
with  the  oral  cavity. 

These  malformations  are  quite  similar  in  character,  but  not 
uniform  in  extent.  They  may  be  said  to  begin  with  the  uvula, 
and  in  the  uvula  and  velum  always  occupy  the  median  line ; 
but  as  the  defect  progresses  anteriorly,  it  may  deflect  to  one 
side  or  the  other  of  the  vomer,  and  follow  the  nasal  passage 
through  the  lips,  leaving  the  vomer  articulated  with  the  pala- 
tine bone  on  one  side ;  while  in  other  cases  the  deformity  seems 
to  follow  the  median  line,  and  thus  involves  both  nasal  pas- 
sages, and  terminates  in  a  double  fissure  of  the  lip. 

*  The  descriptions,  with  accompanying  illustrations,  embraced  in  the 
above  chapter  were  contributed,  at  the  solicitation  of  the  author,  by  Profes- 
sor Norman  W.  Kingsley,  and  may  therefore  be  relied  upon  as  an  authori- 
tative exposition  of  the  most  approved  manipulation  and  appliances  involved 
in  the  practice  of  that  difficult  and  important  specialty  of  the  Dental  Art  in 
which  the  writer  excels. 


PE.  kingsley's  aetifictal  velum  and  palate.     417 

In  both  classes  (accidental  and  congenital)  the  faculty  of  dis- 
tinct articulate  speech  is  seriously  impaired  by  defects  of  any 
extent.  In  ordinary  cases  of  congenital  deformity,  deglutition 
is  not  materially  interfered  with.  The  patient  having  never 
known  any  other  method  of  swallowing,  is  not  conscious  of 
any  difficulty.  Accidental  lesions,  however,  coming  generally 
in  adult  life,  produce,  in  this  respect,  very  great  inconvenience. 
The  remedy  for  these  evils  must  be  the  closing  of  the  abnor- 
mal passage  by  some  means  which  will  restore  the  functions  to 
the  deformed  organs.  In  perforations  of  the  hard  palate, 
unless  of  extraordinary  extent,  the  method  is  very  simple.  In 
the  loss  of  the  soft  palate  by  disease  the  remedy  is  more  diffi- 
cult, and  in  extensive  congenital  deformity  still  more  compli- 
cated appliances  will  be  required. 

As  we  have  classified  the  defects,  we  shall  also  classify  the 
appliances  used  for  their  remedy. 

The  term  obturator  will  be  used  for  all  appliances  intended 
to  stop  a  passage,  as  all  openings  in  the  hard  or  soft  palate 
which  have  a  complete  boundary.  Appliances  made  to  supply 
the  loss  of  the  posterior  soft  palate,  whether  accidental  or  con- 
genital, will  be  called  artificial  vela  or  palates. 

Obturators. — Any  unnatural  opening  from  the  oral  cavity 
into  the  nasal  cavity,  which  will  permit  the  free  passage  of  the 
breath,  will  impair  articulation.  Any  appliance  which  will 
close  such  passage,  and  can  be  worn  without  inconvenience,  will 
restore  articulation.*  Obturators  were  formerly  made  of  me- 
tallic plate,  gold  or  silver  being  most  commonly  employed,  and 
many  very  ingenious  pieces  of  mechanism  were  the  result  of 
such  efforts,  but  latterly  vulcanized  rubber  has  almost  entirely 
superseded  the  use  of  metals.  Vulcanite  has  been  found  pref- 
erable to  metals,  being  much  lighter  and  much  more  easily 
formed  and  adapted,  particularly  when  of  peculiar  shape. 


*  The  Htudent  will  hear  in  mind  that  no  cognizance  is  here  taken  of  open- 
ings similar  to  tliose  descrlhed  in  cases  of  congenital  fissure,  where  the  sur- 
geon has  united  the  soft  palate,  and  left  an  opening  through  the  hard  palate, 
to  be  covered  hy  an  obturator.  In  such  cases,  neither  tlie  surgeon's  opera- 
tion nor  the  obturator  will  prove  of  any  material  advantage. 

27 


418  MECHAlSriCAL   DENTISTRY. 

The  steps  to  be  taken  in  the  formation  of  an  obturator  are 
not  unlike  those  used  in  making  a  base  for  artificial  teeth.  It 
is  essential  that  an  accurate  model  be  obtained  of  the  opening, 
the  adjacent  palatal  surface,  and  the  teeth,  if  any  remain  in 
the  jaw.  For  this  purpose  an  impression  in  plaster  is  the  only 
reliable  means  for  such  an  end.  Care  must  be  used  that  a 
surplus  of  plaster  is  not  forced  through  the  opening,  thus  pre- 
venting the  withdrawal  of  the  impression  by  an  accumulated 
and  hardened  mass  larger  than  the  opening  through  which  it 
passed.  To  avoid  this,  beginners  or  timid  operators  had  better 
take  an  impression  in  the  usual  manner  with  wax;  if  this  is 
forced  through,  it  can  be  easily  removed,  without  injury  to  the 
patient.  From  this  wax  impression  make  a  plaster  model, 
and  upon  this  plaster  model  form  an  impression-cup  of  sheet 
gutta-percha,  with  a  stick,  piece  of  wire,  strip  of  metal,  or  any 
other  convenient  thing  for  a  handle.  This  extemporized  im- 
pression-cup must  not  impinge  upon  the  borders  of  the  open- 
ing, neither  should  it  enter  to  any  extent.  With  a  uniform 
film  of  soft  plaster  of  from  one-sixteenth  to  one-eighth  of  an 
inch  in  thickness  laid  over  this  cup,  a  correct  impression  can 
be  made  without  any  surplus  to  give  anxiety.  Upon  a  correct 
plaster  cast,  taken  from  such  an  impression,  make  a  model  of 
the  obturator  out  of  gutta-percha,  or  any  other  plastic  sub- 
stance, the  subsequent  steps  being  in  principle  the  same  as  in 
making  any  other  piece  of  vulcanite.  It  is  desirable  that  it 
should  enter  the  perforation  and  restore  as  far  as  possible  the 
lost  portion  of  the  palate,  but  it  must  not  protrude  into  or  in 
any  way  obstruct  the  nasal  passage. 

The  entire  freedom  of  the  nasal  passage  is  essential  to  the 
purity  of  articulation. 

That  portion  of  the  obturator  which  occupies  the  oral  cavity 
should  be  made  as  delicate  as  possible,  consistent  with  its 
strength  and  durability. 

A  clumsy  contrivance  will  interfere  with  articulation  almost 
as  much  as  it  is  improved  by  stopping  the  opening ;  therefore 
if  the  obturator  could  be  confined  entirely  to  the  opening,  like 
a  cork  in  a  bottle,  it  would  be  all  the  more  desirable,  but  as  it 


DR.    KIXGSLEY's   artificial    VELUM   AND   PALATE.       419 


cannot,  resort  must  be  had  to  clasping  to  the  contiguous  teeth, 
if  there  are  any,  and  if  not,  the  obturator  must  spread  out  over 
the  whole  jaw,  and  receive  its  support  in  the  same  manner  as 
would  a  set  of  artificial  teeth.  In  fact  this  is  just  what  it 
would  become  in  such  a  case,  viz.,  an  upper  set  of  teeth  bridg- 
ing over  and  filling  up  an  opening  in  the  palate,  thus  combin- 
ing an  obturator  with  a  set  of  teeth. 

Fig.  168  represents  an  obturator  without  teeth  and  without 
clasps,  for  a  perforation  of  the  hard  palate,  being  sustained  in 
situ  by  impinging  upon  the  natural  teeth  with  which  it  comes 
in  contact.     Accuracy  of  adaptation  and  delicacy  in  form  are 


Fig.  168. 


Fig.  169. 


all  that  is  essential  in  such  cases,  and  the  restoration  of  the 
speech  will  follow  immediately. 

Fig.  1G9  rei)resents  a  more  complicated  obturator,  adapted 
to  an  opening  in  the  soft  palate. 

The  necessity  for  a  variation  in  the  plan  will  be  found  in 
the  anatomical  fact  of  the  constaut  muscular  action  of  the  soft 
palate,  which  would  not  permit,  without  irritation,  the  presence 
of  an  immovable  fixture. 

This  is  contrived,  therefore,  with  a  joint,  that  will  permit 
the  part  attached  to  the  teeth  to  remain  stationary,  while  the 
obturat(jr  proper  is  carried  up  or  down  as  moved  by  the  mus- 
cles. The  joint  A  should  occupy  tiie  position  of  the  junction  of 
the  hard  and  soft  palates.  The  joint  and  principal  part  of  the 
applian(;e  is  made  of  gold,  the  obturator  of  vulcanite.  The 
projection  />  lies  like  a  flange  upon  tlie  superior  surface  of  the 
palate,  and  sustains  it;  otherwise  the  mobility  of  the  joint 


420  MECHANICAL   DENTISTRY. 

would  allow  it  to  drop  out  of  the  opening.  This  flange  is 
better  seen  in  the  side  view  marked  C  It  is  readily  placed  in 
position  by  entering  the  obturator  first,  and  carrying  the  clasps 
to  the  teeth  subsequently. 

Figures  168  and  169  will  illustrate  the  essential  principles 
involved  in  all  obturators.  The  ingenuity  of  the  dentist  will 
often  be  taxed  in  their  application,  as  the  cases  requiring  such 
appliances  all  vary  in  form  and  magnitude. 

Artificial  Palates. — Before  proceeding  to  a  description  of 
appliances,  a  brief  reference  to  the  anatomical  relations  and 
functions  of  the  palate  will  be  necessary.  The  palate  exercises 
quite  as  important  an  office  in  the  articulation  of  the  voice  as 
does  the  tongue  or  lips.  Being  a  muscular  and  movable  par- 
tition to  separate  the  nasal  and  oral  cavities,  one  edge  is  attached 
to  the  border  of  the  hard  jjalate,  while  the  other  vibrates  be- 
tween the  pharynx  and  the  tongue.  The  voice,  therefore,  as 
it  issues  from  the  larynx  is  directed  by  the  palate  entirely  into 
the  mouth,  or  through  the  nose,  or  permitted  to  pass  both 
ways. 

A  very  slight  deviation  in  this  organ  from  its  natural  form 
will  make  the  voice  give  a  different  sound.  So  will  also  the 
presence  of  anything  that  clogs  the  natural  passages,  either  oral 
or  nasal. 

Place  any  obstruction  in  the  nasal  passages,  paralyze  the 
soft  palate,  or  let  it  be  deficient  in  size,  and  the  power  of  dis- 
tinct articulation  is  wanting. 

The  evidence  of  this  statement  is  frequently  found  after  the 
surgeon  has  successfully  performed  the  operation  of  staphylor- 
raphy  in  cases  of  congenital  fissure. 

In  such  instances  (with  rare  exceptions)  the  newly  formed 
palate  is  so  deficient  in  length,  and  so  tense,  as  to  be  deprived 
of  its  function.  It  cannot  be  raised  so  as  to  meet  the  pharynx 
and  shut  off  the  nasal  passage,  but  hangs  like  an  immovable 
septum  to  divide  the  column  of  sound. 

Fig.  170  represents  a  defective  palate  belonging  to  the  first 
class ;  the  uvula  and  a  portion  of  the  soft  palate  contiguous 
being  destroyed  by  disease.     In  such  a  case  an  obturator  would 


DE.    KINGSLEY's   artificial    VELUM    AXD    PALATE. 


421 


be  useless ;  the  constant  activity  of  the  surrounding  parts  would 
not  tolerate  it.  The  material  used'  for  a  substitute  must  be 
soft,  flexible,  and  elastic,  and  the  elastic  vulcanite  is  admirably 
adapted  to  this  purpose. 

^  By  observing  the  cut  (Fig.  170)  it  will  be  seen  that  a  por- 
tion of  the  soft  palate  along  the  median  line  remains,  and  con- 
sequently there  will  be  considerable  muscular  movement  which 
must  be  provided  for,  and  which  may  be  taken  advantage  of. 
It  is  desirable  to  make  this  movement  available  in  usine:  an 


Fig.  170. 


artificial  palate,  as  thereby  more  delicate  sounds  are  produced 
than  otherwise. 

This  case  presents  some  extraordinary  difficulties,  in  the  fact 
that  all  the  teeth  of  the  upper  jaw  have  been  extracted,  and 
it  was  neces.sary,  therefore,  to  adapt  a  plate  which  should  not 
only  sustain  teeth  for  mastication  but  bear  the  additional  re- 
6ponsil)ility  of  supporting  the  artificial  palate.  In  the  choice 
of  material  best  adapted  for  the  base  for  the  teeth  in  such  in- 
stances, it  is  preferable  to  adopt  that  which  will  prove  the  most 
durable.  Tliere  are  too  many  interests  involved  to  risk  the 
adoption  of  anything  but  the  best.  In  the  case  under  descrip- 
tion, the  patient  desired  duplicates,  and  two  sets  of  teeth  were 


422 


MECHANICAL  DENTISTEY. 


made,  one  on  gold  and  the  other  on  platina  with  continuous 
gum. 

The  plates  were  made  like  other  sets  of  teeth,  with  the  ex- 
ception of  a  groove  located  on  the  median  line  at  the  posterior 
edge  to  receive  the  attachment  for  the  palate  (marked  C,  in 
Fig.  171). 

Fig.  171  will  indicate  the  set  of  teeth  with  palate  attached. 
The  wings  marked  letters  A  and  B  are  made  of  soft  rubber; 


Fig.  171. 


the  frame  to  support  them  is  made  of  gold,  with  a  joint  to  pro- 
vide for  the  perpendicular  motion  of  the  natural  palate,  as  in 
the  case  of  the  obturator  represented  in  Fig.  169. 

When  the  artificial  palate  is  in  use,  the  joint  and  frame 
immediately  contiguous  lie  close  to  the  roof  of  the  mouth  ;  the 
rubber  wing,  letter  A,  bridges  across  the  opening  on  the  infe- 
rior surface  or  side  next  the  tongue  ;  the  wing,  letter  B,  bridges 
across  the  opening  on  the  superior  or  nasal  surface,  and  is  also 
prolonged  backward  until  it  nearly  touches  the  muscles  of  the 
pharynx  when  they  are  in  repose. 

Both  these  wings  reach  beyond  the  boundary  of  the  opening 
and  rest  on  the  surface  of  the  soft  palate  for  a  distance  of  from 
one-eighth  to  one-quarter  of  an  inch,  thus  embracing  the  entire 
free  edge  of  the  soft  palate.  This  last  provision  enables  the 
natural  palate  to  carry  the  artificial  palate  up  or  down,  as  articu- 
lation may  require. 

When  the  organs  of  speech  are  in  repose,  there  is  an  opening 


DR.    KIXGSLEY's   artificial   VELUM   AND    PALATE.      423 

behind  the  palate  sufficient  for  respiration  through  the  nares. 
When  these  organs  are  in  action,  a  slight  elevation  of  the  palate, 
or  a  contraction  of  the  pharynx,  will  entirely  close  the  nasal 
passage  and  direct  all  the  voice  through  the  mouth.  The  palate 
thus  becomes  a  valve  to  open  or  close  the  nares,  and  to  be  tol- 
erated must  be  made  with  thin  and  delicate  edges  which  will 
yield  upon  pressure.  An  instrument  thus  made  will  restore, 
as  for  as  is  possible  by  mechanism,  the  functions  of  the  natural 
organ. 

In  the  case  under  description  the  patient  was  a  lady ;  the 
defect  had  existed  for  seven  years  before  remedy.  Articulation 

Fig.  172. 


was  very  defective ;  distinct  and  perfect  articulation  followed 
within  one  month. 

Fig.  172  represents  the  artificial  i^alate  separated  into  its 
constituent  parts.  The  frame  is  bent  at  the  joint,  in  the  en- 
graving, to  show  a  stop,  marked  D,  which  prevents  the  appli- 
ance from  dropping  out  of  position.  Letter  C  shows  the  tongue, 
which  enters  the  groove  in  tlie  plate  of  teeth  and  connects  them. 
Letters  A  and  B  are  the  rubber  flaps,  which  are  secured  to  the 
frame  by  the  hooks  as  seen  in  the  engraving. 

The  process  for  making  the  rubber  wings  will  be  found  de- 
scribed on  page  429. 

Fig.  173  shows  a  more  extensive  i)alatine  defect  of  the  first 
cla.s.s.  in  this  ca.se  the  entire  soft  palate  is  gone,  together  with 
a  small  portion  of  the  hard  palate  at  the  median  line. 


424 


MECHANICAL   DENTISTEY. 


Although  this  defect  is  greater  in  extent,  the  means  for  its 
remedy  are  more  simple.  The  muscles  of  the  palate  are  en- 
tirely gone,  and  consequently  no  perpendicular  movement  need 
be  provided  for. 

The  appliance  in  this  case  will  resemble  an  elastic  obturator 
more  than  the  valve-like  palate  of  the  preceding  one.  The 
principle  here  adopted  will  be  substantially  that  recomended 
by  Mr.  Sercombe,  of  London,  some  ten  years  since,  and  con- 


FiG.  173. 


sists  of  a  plate  with  a  set  of  teeth  in  the  usual  form,  and 
attached  to  its  posterior  edge  an  apron  of  soft  rubber,  which 
shall  bridge  the  opening  on  its  inferior  surface,  extending 
nearly  to  the  pharynx.  Fig.  174  represents  the  set  of  teeth 
with  the  palate  attached.  In  Mr.  Sercdmbe's  appliance  this 
apron  was  made  of  the  common  sheet  rubber  in  the  market, 
prepared  for  other  uses,  and  is  objectionable  for  two  reasons: 
1st,  a  want  of  purity  in  the  materials  of  which  it  is  compounded, 
in  many  instances  substances  being  used  in  its  manufacture 
which  would  prove  deleterious  to  the  health  of  the  patient  ; 
and,  2d,  its  uniformity  of  thickness.    It  is  far  preferable,  there- 


DR.    KIXGSLEY's   artificial   VELUM   AND   PALATE.      425 

fore  to  make  a  mould  which  will  produce  a  palate  of  pure  and 
harmless  materials,  and  which  shall  be  of  sufficient  thickness 
in  the  central  part,  and  at  its  anterior  edge,  to  give  it  stability, 
and  shall  have  a  thin  and  delicate  boundary  wherever  it  comes 
in  contact  with  movable  tissue.  Such  a  palate  may  be  made 
in  a  mould  by  substantially  the  same  process  as  hereinafter 

Fig.  174. 


described.  (See  page  429.)  It  may  be  secured  to  the  plate  by 
a  variety  of  simple  means.  One  which  will  give  as  little 
trouble  to  the  patient  as  any  other,  is  to  make  a  series  of  small 
holes  along  the  edge  of  the  plate  and  stitch  it  on  with  silk,  or 
fine  platina,  gold,  or  silver  wire  may  be  used. 

It  is  desirable  to  have  the  plate  and  palate  present  a  uniform 
surface  on  the  lingual  side.  In  fitting  the  plate,  therefore,  it 
may  be  raised  along  the  posterior  edge  from  the  sixteenth  to 
the  tenth  of  an  inch,  according  to  the  thickness  of  palate  de- 
sired. The  rul>ber  will  thus  be  placed  on  the  palatine  surface 
of  the  plate  and  present  uniformity  on  the  lingual  surface. 

A  little  thought  will  show  that  in  this  case  the  patient 
must  educate  the  ramdcH  of  the  pJiarynx  alone  to  do  the  work 
of  shutting  off  the  nares,  which  in  the  former  case  was  per- 
formed by  them  in  conjunction  with  the  muscles  of  the  palate. 


426  MECHANICAL   DENTISTRY. 

Perfection  of  articulation  will  therefore  depend  upon  the  suc- 
cess of  the  patient  in  this  new  use  of  these  muscles. 

In  cases  of  accidental  lesions  of  the  palate,  such  as  are  under 
consideration,  this  education  of  the  muscles  to  a  new  work  will 
not  be  difficult.  The  patient  at  some  former  time  has  had  the 
power  of  distinct  articulation ;  his  ear  has  recognized  in  his 
own  voice  the  contrast  between  his  present  and  former  condi- 
tion, the  ear  will  therefore  direct  and  criticise  the  practice  until 
the  result  is  attained. 

In  the  case  illustrated  by  Figs.  173  and  174,  the  defect  had 
existed  for  twenty-eight  years,  the  patient  at  the  time  of  the 
introduction  of  the  artificial  palate  being  nearly  fifty  years  of 
age.  The  effect  upon  the  speech  was  instantaneous.  Articu- 
lation was  immediately  nearly  as  distinct  as  in  youth,  and  this 
remarkable  distinctness  can  only  be  accounted  for  upon  the 
assumption  that  the  pharyngeal  muscles  had  undergone  a  thor- 
ough training  in  the  vain  eifort  to  articulate  without  any 
palate.* 

The  two  cases  chosen  to  illustrate  the  application  of  artificial 
palates  in  accidental  lesion  have  required,  as  will  have  been 
perceived,  entire  upper  sets  of  artificial  teeth  in  connection 
with  the  palates.  This  selection  was  purposely  made  because 
the  difficulties  to  be  overcome  are  much  greater.  In  cases 
where  there  are  natural  teeth  remaining  in  the  upper  jaw,  the 
palate  and  its  connection  with  a  plate  would  be  substantially 
the  same,  and  the  plate  might  easily  be  secured  to  the  teeth  by 
clasps  in  the  same  manner  as  a  partial  denture. 

Artificial  Palates  for  Congenital  Fissure. — Congenital  fissure 
of  the  palate  presents  far  greater  difficulties  to  be  overcome 
than  cases  of  accidental  lesion.  The  opening  is  commonly 
more  extensive,  the  appliance  more  complicated,  and  the  result 
more  problematical.  Nevertheless,  appliances  have  been  made 
in  a  large  number  of  cases,  which  have  enabled  the  wearer  to 
articulate  with  entire  distinctness,  so  much  so  as  not  in  the 

*  An  account  of  this  case  appears  in  the  Argus,  of  Bainbridge,  Georgia, 
August  1st,  1868,  written  by  the  patient  himself,  who  is  the  editor  of  that 
paper. 


DR.   KINGSLEY's  artificial   VELUM   AND   PALATE.      427 

least  to  betray  the  defect.  The  first  efforts  in  this  direction 
were  of  the  character  of  obturators,  simply  plugs  to  close  the 
posterior  nares,  and  the  results  were  far  from  satisfactory.  It 
was  not  until  it  was  recognized  that  the  two  classes  of  cases 
(accidental  and  congenital)  were  entirely  distinct  that  much 
progress  was  made. 

Nearly  every  case  of  accidental  lesion  can  be  treated  with 
an  obturator  with  considerable  success;  very  rarely  will  an 
obturator  be  of  any  benefit  in  congenital  fissure,  even  if  the 
congenital  and  accidental  case  present  substantially  the  same 
form  of  opening.  For  this  reason  so  much  mystification  has 
been  thrown  around  these  appliances  within  a  few  years  past. 
The  character  of  the  different  classes  has  been  confounded, 
and  an  instrument  admirably  adapted  to  one  class  has  had 
claimed  for  it  an  equal  application  to  the  other  class.  Let  it 
be  understood,  therefore,  as  a  rule  to  which  there  will  be  but 
few  exceptions,  that  congenital  fissure  of  the  soft  palate  re- 
quires for  its  successful  remedy  a  soft,  elastic,  and  movable 
appliance,  and  that  when  the  most  skilfully  made  and  adapted 
instrument  is  worn,  articulation  must  be  learned,  like  any 
other  accomplishment.  Various  inventions  have  been  made 
for  this  purpose  within  the  last  twenty-five  years,  from  the 
most  complicated  one  of  Mr.  Stearns,  described  in  the  first 
edition  of  this  work,  to  the  extreme  of  simplicity  of  bridging 
the  gap  with  a  simple  flap  of  rubber.  The  Stearns  instru- 
ment, with  all  its  complexity,  embodied  the  only  true  principle, 
viz.,  the  rendering  available  the  muscles  of  the  natural  palate 
to  control  the  movements  of  the  artificial  palate. 

The  essential  requisites  of  an  artificial  palate  will  be,  to 
restore  as  far  as  possible  the  natural  form  to  the  defective 
organs  with  such  material  as  shall  restore  their  functions. 
Muscular  power,  certainly,  cannot  be  given  to  a  piece  of  mecha- 
nism, but  the  material  and  form  may  be  such  that  it  will  yield 
to  and  be  under  the  control  of  the  muscles  surrounding  it,  and 
thus  measurably  bestow  upon  it  the  function  of  the  organ 
which  it  represents. 

Fig.  175  represents  a  model  of  a  fissured  i)alate,  complicated 


428 


MECHANICAL   DENTISTEY. 


with  harelip  on  the  left  of  the  mesial  line.  There  is  a  division 
also  of  the  maxilla  and  the  alveolar  process,  the  sides  being 
covered  with  mucons  membrane  which  come  in  contact  with 


Fig.  175. 


each  other,  but  are  not  united.     The  left  lateral  incisor  and 
left  canine  tooth  are  not  developed. 

Fig.  176  represents  the  artificial  velum,  as  viewed  from  its 
superior  surface,  together  with  the  attachment  and  two  artifi- 
cial teeth  to  fill  the  vacancy. 


Fig.  176. 


The  lettered  portion  of  this  appliance  is  made  of  elastic  vul- 
canized rubber ;  its  attachment  to  the  teeth  of  hard  vulcanized 
rubber,  to  which  the  velum  is  connected  by  a  stout  gold  pin, 
firmly  imbedded  at  one  end  in  the  hard  rubber  plate.     The 


DR.   KI^'GSLEY'S   ARTIFICIAL   VELUM   AND   PALATE.      429 

other  end  has  a  head,  marked  C,  which  being  considerably 
larger  than  the  pin,  and  also  the  corresponding  hole  in  the 
velum,  it  is  forced  through, — the  elasticity  of  the  velum  per- 
mitting,— and  the  two  are  securely  connected. 

The  process,  B,  laps  over  the  superior  surface  of  the  maxilla 
(the  floor  of  the  naris),  and  effectually  prevents  all  inclination 
to  droop. 

The  wings  A  A,  reach  across  the  pharynx,  at  the  base  of  the 
chamber  of  the  pharynx,  behind  thQ  remnant  of  the  natural 
velum. 

The  wings  D  D,  rest  upon  the  opposite  or  anterior  surface 
of  the  soft  palate. 

Fig.  177  represents  a  model,  the  same  as  Fig.  175,  with  the 
appliance,  Fig.  176,  in  situ. 


Fig.  177. 


,,-j,^;^^ 


The  wing  D  D,  in  Fig.  176,  and  the  posterior  end  of  the 
artificial  velum  only  in  this  cut  being  visible. 

Method  of  Making  an  Artificial  Palate. — The  success  of 
these  ap})liances  dej)ends  very  much  upon  the  accuracy  of  the 
model  obtained  to  work  by. 

It  is  essential  that  the  entire  border  of  the  fissure  from  the 
apex  to  the  uvula  should  be  perfectly  represented  in  the  model, 


430  MECHANICAL  DENTISTEY. 

as  the  parts  are  when  in  repose.  It  is  also  necessary  that  the 
model  show  definitely  the  form  of  the  cavity  above,  and  on 
either  side  of  the  opening  through  the  hard  palate,  being  that 
part  of  the  cavity  which  is  hidden  from  the  eye.  It  is  desir- 
able, also,  that  the  posterior  surface  of  the  remains  of  the  soft 
palate  be  shown,  but  this  is  not  essential ;  but  it  is  especially 
important  that  the  anterior  or  under  surface  be  represented 
with  relaxed  muscles  and  in  perfect  repose.  The  impression 
for  such  a  model  must  be  taken  in  plaster ;  it  is  the  only  ma- 
terial now  in  use  adapted  to  the  purpose.  An  ordinary  bri- 
tannia  impression-cup  may  be  used,  selecting  one  in  size  and 
form  corresponding  to  the  general  contour  of  the  jaw.  This 
cup  will  be  found  too  short  at  the  posterior  edge  to  receive  the 
soft  palate,  but  it  may  be  extended  by  the  addition  of  a  piece 
of  sheet  gutta-percha,  which  must  be  moulded  into  such  form 
as  not  to  impinge  upon  the  soft  palate,  but  which  will  reach 
under  and  beyond  the  uvula,  and  thus  protect  the  throat  from 
the  droppings  of  plaster.  Before  using  the  plaster  the  posterior 
edge  of  the  gutta-percha  extension  may  be  softened  by  heat 
and  introduced  into  the  mouth  ;  contact  with  the  soft  palate 
will  cause  it  to  yield,  so  that  there  is  no  danger  of  its  forcing 
away  the  soft  tissues  when  the  plaster  is  used.  With  the  pre- 
caution not  to  use  too  much  plaster,  the  first  effort  will  be  to 
get  only  the  lingual  surface.  After  trial,  if  the  impression 
show  definitely  the  entire  border  of  the  fissure,  and  the  soft 
palate  has  not  been  pushed  up  by  contact  with  the  cup,  nor 
pulled  up  by  the  spasmodic  action  of  the  levator  muscles,  it  is 
all  that  is  thus  far  desired.  If,  however,  the  soft  parts  have 
been  disturbed  (which  on  close  comparison  a  little  experience 
will  decide),  it  is  better  to  cast  a  model  into  the  impression, 
and  upon  this  model  extemporize  an  impression-cup  as  de- 
scribed on  page  418.  This  temporary  cup  will  have  the 
advantage  of  the  former,  insomuch  that  it  will  require  but  a 
film  of  plaster  to  accomplish  the  result,  thus  lessening  the 
danger  of  disturbing  the  soft  tissues.  After  the  removal,  if  it 
is  seen  that  any  surplus  has  projected  through  the  fissure  and 
lapped  out  to  the  floor  of  the  nares,  it  may  be  pared  off. 


DE.   KINGSLEy's   artificial  VELUM   AND   PALATE.       431 


The  next  step  will  be  to  obtain,  in  conjunction  with  tliis 
impression  of  the  under  surface,  which  we  will  call  the  palatal 
impression,  an  impression  of  the  upper  or  nasal  surface  of  the 
hard  palate. 

This  can  be  done  by  filling  the  cavity  above  the  roof  of  the 
mouth  wnth  soft  plaster  down  to  the  border  of  the  fissure,  and 
while  yet  very  soft  carrying  immediately  the  palatal  impres- 
sion against  it,  and  retaining  it  in  that  position  until  the  plaster 
is  hard,  which  can  easily  be  ascertained  by  the  remains  in  the 
vessel  from  which  it  was  taken.  With  the  precaution  to  paint 
the  surface  of  the  palatal  impression  with  a  solution  of  soap, 
to  prevent  the  two  masses  from  adhering  when  brought  in  con- 
tact, there  will  be  no  difficulty  in  removing  it  from  the  mouth. 


Fig.  178. 


leaving  the  mass  which  forms  the  nasal  portion  in  situ.  AYith 
a  suitable  pair  of  tweezers  this  mass  is  easily  carried  backward 
and  withdrawn  from  the  mouth,  and  the  irregular  surface  of  con- 
tact indicates  its  relation  to  its  fellow  when  brouglit  together. 

Fig.  178  will  show  such  an  impression.  The  portion  marked 
A,  B,  C,  will  readily  be  distinguished  as  that  which  entered 
the  nasal  cavity.  The  line  of  separation  from  the  palatal  im- 
pression is  plainly  indicated  in  the  engraving.  The  groove, 
marked  D,  shows  clearly  the  impression  made  by  the  delicate 
uvula  in  the  soft  plaster.  The  nasal  portion  is  relatively  large, 
showing  an  unusually  large  nasal  cavity. 

The  vomer  lies  between  the  projections  marked  A  A ;  these 
projections  entering  the  nasal  passages.  The  surfaces  marked 
B  B,  came  in  contact  witli  the  middle  turbinated  bones;  the 


432 


MECHANICAL   DENTISTRY. 


surface  marked  C  in  contact  with  the  inferior  turbinated  bone. 
In  many  instances  these  turbinated  bones  are  so  large  as  to 
nearly  fill  the  nasal  passages. 

The  method  of  obtaining  the  model  of  the  jaw  from  the  im- 
pression does  not  require  any  particular  description.  The 
process  is  similar  to  the  making  of  a  cast  into  any  other  mouth 
impression. 

The  model  represented  in  Fig.  175  shows  a  convenient  form 
for  such  a  cast. 

When  the  nasal  portion  of  the  impression  does  not  indicate 
the  superior  surface  of  the  soft  palate,  the  part  may  be  repre- 


FlG.  179. 


sented  in  the  cast  by  carving.  It  is  not  essential  to  the  success 
of  the  instrument  to  be  made  that  the  posterior  surface  of  the 
soft  palate  should  be  represented  with  the  same  accuracy  that 
is  required  of  the  inferior  surface,  or  of  both  surfaces  of  the 
hard  palate.  By  the  aid  of  a  small  mirror  and  a  blunt  probe, 
the  thickness  of  the  velum  and  the  depth  behind  the  fissure  can 
be  ascertained  and  the  model  carved  accordingly. 

The  portion  of  the  artificial  palate  coming  in  contact  with  it 
is  so  elastic  that  it  easily  adapts  itself  to  a  slight  inequality, 
rendering  absolute  accuracy  less  important. 


DE.   KINGSLEY's  artificial  VELUM   AND   PALATE.      433 

The  next  step  will  be  the  formation  of  a  model  or  pattern 
of  the  palate.  Sheet  gutta-percha  is  preferable  for  this  pur- 
pose, although  wax,  or  many  other  plastic  substances,  might 
answer. 

The  form  which  should  be  given  it  is  better  indicated  by 
the  drawings.  Figs.  176  and  183,  than  a  written  description 
would  give.     The  Stearns  instrument,  of  which  a  cut  is  here 

Fig.  180. 


given  (Figs.  179,  180),  was  made  to  embrace  the  edges  of  the 
fissure,  and  was  slit  up  through  the  middle,  so  that  when  the 
edges  of  the  fissure  approach  each  other,  as  they  always  do  in 
swallowing,  the  two  halves  of  the  instrument  would  slide  by 
each  other,  and  a  third  flap  or  tongue  was  made  and  supported 
by  a  gold  spring  to  cover  and  keep  closed  this  central  slit. 
This  complicated  provision  for  the  contraction  of  the  fissure 
is  entirely  superseded  in  Figs.  176  and  183,  by  making  the 
instrument  somewhat  in  the  form  of  two  leaves,  one  to  lie  on 
the  inferior  and  the  other  upon  the  superior  surface  of  the  pal- 
ate, and  joined  together  along  tiie  median  line.  When  the 
fissure  contracts  the  halves  of  the  divided  uvula  slide  toward 

28 


434  MECHANICAL   DENTISTRY. 

each  other  between  these  two  leaves.  The  posterior  portion, 
marked  A  in  Fig.  176,  is  made  very  thin  and  delicate  on  all 
its  edges,  as  it  occupies  the  chamber  of  the  pharynx,  and  is 
subject  to  constant  muscular  movement. 

The  sides  are  rolled  slightly  upward  while  the  posterior  end 
is  curved  downward.  The  inferior  portion  marked  D  D,  in 
Fig.  176,  should  reach  only  to  the  base  of  the  uvula,  and 
bridge  directly  across  the  chasm  at  this  point,  and  no  effort  to 
imitate  the  uvula  should  be  made.  The  extreme  posterior  end 
should  not  reach  the  posterior  wall  of  the  pharynx  when  all 
the  muscles  are  relaxed  by  a  quarter  of  an  inch,  although  sub- 
sequent use  must  determine  whether  this  space  be  increased  or 
diminished,  thus  leaving  abundant  room  for  respiration  and 
the  passage  of  nasal  sounds.  In  cases  where  it  is  desirable  to 
make  the  instrument  independent  of  the  teeth,  as  far  as  possi- 
ble, in  its  support,  the  anterior  part  which  occupies  the  apex 
of  the  fissure  in  the  hard  palate  may  lap  over  on  to  the  floor 
of  one  or  both  nares.  Such  a  projection  is  seen  in  Fig.  176, 
marked  B,  and  a  like  process  is  seen  in  Fig.  183,  but  not  let- 
tered. Were  it  not  for  this  process  in  this  case,  the  palate 
would  drop  out  of  the  fissure  into  the  mouth,  the  single  clasp 
at  the  extreme  anterior  end  not  being  sufficient  to  keep  the 
whole  appliance  in  place  throughout  its  entire  length.  Caution 
must  be  exercised  that  this  projection  entering  the  nares  be  not 
too  large,  or  it  will  obstruct  the  passage  and  give  a  disagreeable 
nasal  tone  to  the  voice. 

All  these  described  peculiarities  must  be  provided  for  in  the 
gutta-percha  model,  which,  after  having  been  carefully  formed 
to  the  cast,  may  be  tried  in  the  mouth  to  ascertain  its  length 
or  necessary  variations.  When  its  ultimate  form  has  been  de- 
cided upon,  provision  must  be  made  to  duplicate  it  in  soft 
rubber. 

A  parallel  process,  and  one  which  will  be  a  familiar  illus- 
tration, is  used  when  a  set  of  teeth  is  made  on  vulcanite  base. 
A  model  or  patern  form  is  made  of  gutta-percha,  bearing  the 
teeth,  and  in  all  its  prominent  characteristics  is  shaped  as  the 
completed  denture  is  desired ;  the  rubber  duplicate  being  vul- 


DR.    KINGSLEY'S   AETIFICIAL    VELUM    AND    PALATE.      435 

canized  in  a  plaster  mould.  In  like  manner  the  rubber  dupli- 
cate of  the  palate  as  before  described  may  be  made  in  a  plaster 
mould. 

If  plaster  is  used  it  must  be  worked  with  much  care  so  that 
the  surface  shall  be  free  from  air-bubbles,  or  the  rubber  palate 
will  be  covered  with  excrescences  that  cannot  be  readily  re- 
moved. By  covering  the  surfiice  of  the  mould  with  collodion 
or  liquid  silex,  it  will  be  much  improved.  But  ordinarily 
plaster  moulds  will  be  found  too  troublesome  for  general  use. 
They  may  be  put  to  a  most  excellent  use,  however,  by  using 
one  to  make  a  duplicate  of  the  gutta-percha  in  hard  rubber. 

This  is  not  necessary  with  those  who  have  had  much  expe- 
rience, but  w^ith  beginners  it  will  be  difficult  to  work  up  the 
gutta-percha  as  nicely  as  may  be  desired  ;  a  duplicate  of  vul- 
canite will  enable  the  operator  to  make  a  more  artistic  model 
of  the  palate,  and  one  wliich  can  be  handled  wdth  greater  free- 
dom. 

Fig.  181. 


As  in  the  course  of  a  lifetime  a  considerable  number  of 
elastic  palates  will  be  required,  the  mould  which  produces  them 
should  be  made  of  some  durable  material.  The  type  metal 
of  commerce  is  admirably  adapted  to  this  use.  The  most  com- 
plete mould  is  one  made  of  four  pieces,  which  will  produce  a 
palate  of  one  continuous  piece.  Such  a  mould  requires  very 
nice  mechanical  skill  in  fitting  all  the  parts  accurately,  and 
unless  the  operator  lias  had  experience  in  such  a  direction  it  is 
better  to  simplify  the  matter.  By  making  the  palate  in  two 
pieces,  to  be  joined  after  vulcanizing,  the  mould  may  be  made 
in  two  pieces  and  with  very  little  trouble. 

Fig.  181  shows  a  palate  divided. 


436 


MECHAlSriCAL   DENTISTRY. 


Fig.  182  shows  the  mould  or  flask  in  which  it  is  vulcanized. 
These  flasks  were  made  expressly  for  this  purpose,  but  they 
are  not  so  unlike  the  flasks  in  common  use  in  dentists'  labora- 


FlG.  182. 


tories,  that  the  latter  will  not  answer.     The  common  flask  is 
simply  unnecessarily  thick  or  deep. 

The  mould  is  readily  produced  in  the  following  manner : 
Imbed  the  two  pieces  of  the  palate  in  plaster,  in  one-half  of 
the  flask;  when  the  plaster  is  set  and  trimmed  into  form, 


Fig.  183. 


duplicate  it  in  type-metal  by  removing  the  palate,  varnishing 
the  surface,  moulding  in  sand,  and  casting.  In  making  the  sand 
mould  take  a  ring  of  sheet-iron  of  the  same  diameter  of  the 
flask  and  three  or  four  inches  high ;  slip  it  over  the  flask  and  pack 
full  of  sand.  Separate  them,  remove  the  plaster,  return  the 
flask  to  the  sand  mould,  and  fill  with  the  melted  metal  through 
a  hole  made  in  the  side  or  bottom  of  the  flask.     With  one- 


DE.    KIXGSLEY's   artificial   VELUM   AND   PALATE.      437 

half  thus  made,  substantially  the  same  process  will  produce 
the  counterpart. 

Fig.  183  shows  the  palate  complete  with  its  attachment  to 
the  teeth.  The  palate  is  secured  to  the  plate  by  a  pin  of  gold 
passing  through  a  hole  in  the  palate  of  the  same  size;  the  head 
on  the  pin  being  larger  than  the  hole  is  forced  through,  and 
thus  the  two  halves  of  the  palate  are  bound  together  and  joined 
to  the  plate. 

Fig.  184  shows  a  mould  in  four  pieces.  The  blocks  C  C, 
are  accurately  adapted  to  the  body  of  the  mould,  marked  A, 

Fig.  184. 


and  are  prevented  from  coming  improperly  in  contact  with  each 
other  by  the  flanges  D  D,  which  overlap  the  rest  upon  the 
sides  of  the  main  piece.  B  shows  the  top  of  the  mould,  and 
the  groove  E  provides  for  the  surplus  rubber  in  packing. 

Such  a  mould  makes  the  most  perfect  appliance  that  can  be 
produced.  The  palate  is  one  homogeneous  and  inseparable 
piece.  The  cut  will  sufficiently  indicate  the  forms  of  tlie  several 
parts.  Each  of  these  pieces  is  first  made  in  plaster  of  exactly 
the  form  of  which  the  type-metal  is  desired.  They  are  then 
moulded  in  sand  and  the  type-metal  castas  in  making  an  ordi- 
nary die  for  swaging.  When  in  use,  a  clamp  similar  to  Fig. 
185  is  placed  around  the  mould  to  keep  the  several  parts  firm 
in  their  position. 


438 


MECHAlSriCAL   DENTISTRY. 


The  packing  of  the  mould  with  rubber  will  be  done  in  the 
same  manner  as  when  hard  rubber  is  used  for  teeth  bases;  with 
which  process  it  is  assumed  that  the  operator  is  familiar.  By- 
washing  the  surface  of  the  mould  with  a  thick  solution  of  soap 
previous  to  packing,  the  palate  will  be  more  easily  removed 
after  vulcanizing. 


Fig.  185. 


The  rubber  used  for  this  purpose  must  be  a  more  elastic  com- 
pound than  that  used  as  a  base  for  teeth.  The  composition  used 
for  the  elastic  fabrics  of  commerce  will  answer  if  made  of 
selected  materials. 

The  American  Hard  Rubber  Company  have  recently  placed 
on  sale  at  the  dental  depots  a  compound  admirably  adapted  to 
this  purpose.  The  best  results  are  obtained  when  the  process 
of  vulcanizing  is  carried  from  a  heat  of  230°  gradually  during 
four  or  five  hours  up  to  and  terminating  at  270°. 


INDEX. 


PAGE 

Air-chamber,  manner  of  forming, 229 

Alloys  of  gold  for  dental  purposes,       .         .         .       '.        .         ,         .54 

Alloys  of  copper, 88 

silver, 76 

platinum, 81 

Aluminum, 83 

alloys  of, 85 

Antagonizing  model  for  partial  dentures, 231 

entire  dentures,       ......  255 

upper  dentures,       ......  258 

block-teeth, 292 

Anatomical  articulator,  Bonwill's, 260 

Antimony, 91 

Application  of  heat, 17 

Articulators, 259 

Artificial  dentures, 97 

Artificial  palates, 420 

Artificial  palates  for  congenital  fissures, 426 

Atmospheric  pressure  plates,        ........  227 

Attaching  teeth  to  metallic  base  with  rubber  or  celluloid,    .         .         .  400 

Baking  furnace, 29 

Bismuth, 91 

Block-teeth, 285 

composition  and  preparation  of  body  for, ....  285 

crown  enamel  for,    .         .  287 

gum  enamel  for,       .         .  290 

Babbitt  metal, 142 

Blowpipe, 17 

oxygen,          ..........  17 

oxy-iiydrogen,       .........  17 

mouth, 18 

Ijcllows, 22 

Blank,  celluloid, 384 

Bla.st  furnace, 32 

Bonwill's  method  of  attaching  artificial  crowns, 172 

Brass, 88 

Brass  solder, 88 

Carved  l>lock-tecth, 298 


440  INDEX. 


PAGE 

Celluloid  base, 377 

processes  pi-eliminary  to  moulding,        .        .         .      •  •        .  380 

blank,  selection  and  preparation  of, 384 

moulding  in  hot  moist  air  (dry  heat), 387 

glycerin,    ........  390 

steam, 392 

Chappell's  method  of  attaching  artificial  crowns,          ....  187 

Charcoal, 36 

Clasps, 200 

Cleveland's  air-chamber, 250 

Coke, , 36 

Components  of  dental  porcelain, 277 

Continuous  gum  work, 307 

Dr.  Allen's  methods, 311 

Dr.  Hunter's  formulas  and  methods,          .        .  318 

Dr.  Haskell's  methods, 325 

Dr.  Field's  methods, 330 

application  to  partial  sets,         .         .         .         .  333 

Congenital  defects  of  the  palate, 416 

Converting  gold  alloys  into  required  forms  for  dental  purposes,  .        .  68 

Counter-die, •  135 

Copper, 87 

alloys  of, 87 

Crucibles,      .      _ ,40 

Crucirjg  or  biscuiting, .         .  299 

Darby's  method  of  attaching  artificial  crowns,      ....      159-197 

Dental  porcelain,  components  of, 277 

Dentures,  partial,          .         . 224 

entire,  . 246 

Defects  of  the  palatal  organs, 134 

Dipping, 134 

Diseased  conditions  of  the  mucous  membrane  and  gums,     .         .        .  102 
Diseased  remains  of  teeth,    .         .         .         .         .         .         .         .         .103 

Dies, ,       ...  128 

essential  properties  of, .         .         . 136 

Draw-plate, 74 

DraBght  or  wind  furnace, .28 

Duplicating  a  set  of  teeth  on  rubber, 374 

Entire  dentures, .         .        .  246 

Essential  properties  of  a  die, 136 

Elements  employed  in  refining  gold, 48 

Felspar, 277 

Fitting  pivot  crown, 151 

Flasks,  vulcanite, 350, 352, 353 

Formulas  for  silver  solder, 78 

gold  plate, 55 

clasps,  stays,  etc., 57 

Forging,       .        .        ."       . 70 

Fuel,     .         .         .         .        . 35 

Foster's  method  of  attaching  artificial  crowns, 166 

Furnaces, 28 

Fusible  alloys, 142 

table  of, 143 


INDEX.  441 


PAGE 

Gas  furnace  without  blast,    .........  31 

General  properties  of  alloys,  and  their  treatment  and  behavior  in  the 

process  of  compounding, 93 

German  silver, gg 

Gold, 41 

geological  situations  of,         ........  41 

geographical  distribution  of, 42 

properties  of, 42 

influence  of  alloying  on  the  properties  of, 43 

properties  of  particular  alloys  of, .45 

refining,        ...........  48 

separation  of  foreign  metals  from, 49 

alloy  cast  base, .  407 

crown  faced  with  porcelain, 164 

solders, 57 

wire, 73 

Gutta-percha, 112 

Hand  furnace, 38 

Hawes's  moulding  flask, 129 

Impression  in  wax  for  partial  upper  dentures, 106 

partial  lower  dentures, 109 

entire  upper  dentures, 110 

entire  lower  dentures, 112 

Impression  in  plaster  for  entire  upper  dentures, 118 

entire  lower  dentures, 120 

partial  upper  dentures,  .         .         .         ,11.5 

India-rubber, 33(3 

general  properties  of, 336 

compounding, 338 

method  of  constructing  an  entire  denture  in  a  base  of,    .  338 

formation  of  the  mould  or  matrix, 342 

packing  the  mould, 347 

Influence  of  alloying  on  the  properties  of  gold, 43 

Ingot  moulds, 68 

Kaolin, 278 

Kingsley's  artificial  velum  and  palate, 416 

Laminating  or  rolling, 70 

Lampg, .26 

oil, !        '.      26 

spirit, 27 

Lead, 89 

Malleability  of  gold, 44 

Manner  of  a.scertaining  carat  of  gold  alloys, 59 

reducing  gold  to  a  re<piired  carat, 60 

reducing  gold, 61 

Manufacture  of  jjorcelain  teeth, 279 

Metallic  dies  anil  counter-dies, 128 

Manner  of  obtaining  a  die, 128 

procuring  an  ingot, 68 

Materials  employed  in  obtaining  impressions  of  the  mouth,         .         .  105 

Metallic  clasps  attached  to  rubber  plates, 369 


442  INDEX. 


PAGE 

Method  of  constructing  spiral  springs,  .         .         .         .        .        .        .  271 

obtaining  gold  wire, 73 

Models, 121 

Modifications  in  the  form  of  clasps, 205 

plates  for  entire  upper  dentures,      .         .  249 

entire  lower  dentures,      .        .  253 

partial  dentures,       .         .         .  209 

Moulding, 128 

Moulding  flask,  Hawes's, 129 

Moutli  blowpipe, '18 

Oil  lamp, 26 

Obturators, 417 

Palatal  defects, 416 

Partial  dentures, .  145 

dentures  in  a  base  of  rubber, .  368 

or  stay  clasp,    ..........  208 

dentures  secured  by  clasps, 200 

dentures  supported  by  cylinders  of  wood,         ....  221 

Pivoting  artificial  crowns,     .........  145 

Pivot  plate, 158 

Pivots  of  metal  and  wood,     .........  155 

Pivoting  partial  plates  to  the  roots  of  the  natural  teeth,       .         .        .  224 

Platinum, 79 

alloys  of, 81 

Platinoid  metals,  ...........  81 

Plaster  models, 121 

of  Paris, 113 

Porcelain  block-teeth, 285 

Preparation  of  root  for  pivot  tooth,       .......  147 

Properties  of  particular  alloys  of  gold, 45 

gold, 42 

Producing  continuous  blast  with  mouth  blowpipe,        ....  21 

Pefining  gold, 48 

Removal  of  salivary  calculus, 101 

Reduction  of  silver  to  required  forms  for  use, 77 

Remarks  on  the  use  of  clasps, 200 

Reduction  of  gold  solders  to  proper  forms  for  use,        ....  73 

Reducing  gold  to  a  higher  or  lower  standard  of  fineness,      ...  59 

Required  fineness  of  gold  plate, 54 

Reducing  metals, .54 

Rei^airing  vulcanite  work,    .         .         .         .         .         .         .        .        .  371 

Refitting  gold  or  rubber  plates  with  rubber  lining,       ....  372 

Richmond's  method  of  attaching  artificial  crowns,        ....  185 

Rimming  plate, .  269 

Rose's  fusible  metal, 90 

Rolling  or  laminating,  .         .         .         .         .         .         .         .        .70 

Rolling  mills,        . 70 

Sand,  for  moulding, 128 

Scalloped  clasp, 208 

Separation  of  foreign  metals  from  gold, 49 

Separation  of  teeth  for  clasps, 204 

Sheet-iron  furnace, 38 


INDEX.  443 


PAGE 

Silver, 76 

general  properties  of, 76 

alloys  of,     ...........  76 

Silver  solder, 78 

Silex !        ".         .  277 

Soft  solder,    ............  90 

Spirit-lamp,  ............  27 

Spiral  springs,       •••......,.  271 

Standard  clasp, 207 

Stay  chi-sp,     ." !        !  208 

Steam  gauge, 365 

Substitution  of  plate  for  rubber  teeth, 37O 

Supports, .'        .'  38 

Surgical  treatment  of  the  mouth  after  the  extraction  of  teeth,      .         .  102 

Table  of  coinage  of  different  nations,    . 63 

Teeth  to  which  it  is  most  proper  to  attach  clasps,         ....  202 

Thickness  of  plate  for  clasps,  stays,  etc., 73 

Tin, .'        ."  90 

Time  necessary  to  elapse  before  insertion  of  artificial  dentures,    .         .  103 
Treatment  of  the  mouth  preparatory  to  tlie  insertion  of  artificial  den- 


tures. 


97 


Type  metal, J42 

Uniting  plate  and  clasps, 216 

Varnish,        •••••......  126 

Vulcanite  base,     •••.......  336 

Vulcanizing,  ........  '     354 

Vulcanizers, [         [       354,355,356,307 

Wax, '   ....     105 

yellow, 105 

white, 2Q5 

Webb's  method  of  attaching  artificial  crowns,       ....      161-189 
Wood  pivots, '        *  152 

Zinc, 00 


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The  Clinic. 

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sion."— St.  Louis  Medical  and  Surgical  Journal, 


SECOND  EDITION,  ENTIRELY  RE-WRITTEN, 

WITH  THEIR  TREATMENT ;  INCLUDING  THE  GOUTY  HEART. 

By  J.  MILNER  FOTHERGILL,  M.D., 

Author  of  "  The  Practitioner's  Handbook  of  Treatment,"  "  The  Antagonism  of  Therapeutic  Agents,"  ete. 
OCTAVO.    PRICE,  $3.50. 

"  It  is  the  best,  as  well  as  the  most  recent  work  on  the  subject  in  the  English  language." — 
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"To  many  an  earnest  student  it  will  prove  a  light  in  darkness;  to  many  a  practitioner  cast 
down  with  a  sense  of  his  powerlessness  to  cope  with  the  rout  and  demoralization  of  Nature's 
forces,  a  present  help  in  time  of  trouble." — Philadelphia  Medical  Times. 

"  The  work  throughout  is  a  masterpiece  of  graphic,  lucid  writing,  full  of  good  sound  teaching, 
which  will  be  appreciated  alike  by  the  practitioner  and  the  student." — Student's  Journal. 

"  Dr.  Fothergill's  intention  has  rather  been  to  present  the  natural  history  of  heart  disease  as  a 
series  of  vivid  pictures  before  the  imagination  of  the  reader,  and  to  carry  the  doctor  as  a  living 
actor  into  tlie  scene.  For  this  purpose  he  has  properly  chosen  to  use  academic  detail,  not  ex- 
haustively, but  as  a  means  to  this  end,  and  he  has  brilliantly  succeeded." —  Westminster  Review. 

"  The  most  interesting  chapter  is  undoubtedly  that  on  the  gouty  heart,  a  subject  which  Dr. 
Fothergill  has  specially  studied,  and  on  which  he  entertains  views  such  as  are  likely,  we  think,  to 
be  generally  accepted  by  clinical  physicians,  although  they  have  not  before  been  stated,  so  far  as 
we  are  aware,  with  the  same  breadth  of  view  and  extended  illustration." — British  Med.  Journal. 

"  Dr.  Fothergill's  remarks  on  rest,  on  proper  blood  nutrition  in  heart  disease,  on  the  treat- 
ment of  the  sequelse  of  it,  and  on  the  actions  of  special  medicine,  all  indicate  that,  in  studying 
the  pathology  of  heart  disease,  he  has  earnestly  kept  in  view  rhe  best  means  of  mitigating  suf- 
fering and  of  prolonging  life." — The  Lancet. 

LINDSAY  &  BLAKISTON,  Publishers, 


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THE  SCIENCE  AND  PRACTICE  OF  MEDICINE.  THIRD 
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gregate almost  to  a  volume  of  new  matter,  included  iu  which  will  be  found  the  adoption  and 
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and  the  j>resent  state  of  science.  PVjr  the  practitioner  it  will  be  found  equally  acceptable  as 
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ALLINGHAM  (william),  F.  R.  C.  S., 

Surgeon  to  St.  Mark's  Hospital  for  Fistula,  &.c, 

FISTULA,  IlyEMORRHOIDS,  PAINFUL  ULCER,  STRICT- 
URE, PROLAPSUS,  and  other  Diseases  of  the  Rectum,  their  Diagnosis 
and  Treatment.  Third  Edition,  Revised  and  Enlarged  by  the  Author. 
Octavo.     Price  .         .         .         .         .         .         .         .  .         $3- 00 

This  book  has  been  well  received  by  the  Profession  ;  the  first  edition  sold  rap- 
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chiefly  a.s  to  the  mode  of  treatment. 

The  Medical  J'regx  and  Circular,  speaking  of  it,  says:  "No  book  on  this  special  subjcci 
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ATTHILL  (lombe),  M.  D., 

Fellow  and  Examiner  in  JVlidwifery,  King  and  Queen's  College  of  Physicians,  Dublin. 

CMNICAL  LECTURES  ON  DISEASES  PECULIAR  TO  WO- 
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The  value  and  popularity  of  this  book  is  proved  by  the  rapid  sale  of  the  first  edition, 
which  was  exhausted  ia  less  than  a  year  from  the  time  of  its  publication.  It  appears  to 
possess  three  great  merits  :  First,  It  treats  of  the  diseases  very  common  to  females.  Second; 
It  treats  of  them  in  a  thoroughly  clinical  and  practical  manner.  Third,  It  is  concise,  orig- 
inal, and  illustrated  by  numerous  cases  from  the  author's  own  experience.  His  style  is  clear 
and  the  volume  is  the  result  of  the  autlior's  large  and  accurate  clinical  observation  recorded" 
in  a  remarkable,  perspicuous,  and  terse  manner,  and  is  conspicuous  for  the  best  qualities  0^ 
a  practical  guide  to  the  student  aad  practitioner.  —  British  Medical  Journal. 

ADAMS  (WILLIAM),  F.R.  C.S., 

Surgeon  to  the  Royal  Orthopedic  and  Great  Northern  Hospitals. 

CLUB-FOOT:  ITS  CAUSES,  PATHOLOGY,  AND  TREAT^ 
MENT.  Being  the  Jacksonian  Prize  Essay  of  the  Royal  College  of 
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Regius  Professor  of  Surgery  in  the  University  of  Dublin,  &.C.,  &c. 

RHEUMATIC  GOUT,  or  CHRONIC  RHEUMATIC  ARTHRI- 
TIS OF  ALL  THE  JOINTS.  The  Second  Edition.  Illustrated  by 
numerous  Woodcuts,  and  a  quarto  Atlas  of  Plates.  2  Volumes. 
Price    . ^7-5c> 

ALTHAUS  (JULIUS),  M.D., 

Physician  to  the  infirmary  of  Epilepsy  and  Paralysis. 

A  TREATISE  ON  MEDICAL  ELECTRICITY,  Theoretical  and 

Practical,  and  its  Use  in  the  Treatment  of  Paralysis,  Neuralgia,  and  other 
Diseases.  Third  Edition,  Enlarged  and  Revised,  with  One  Hundred 
and  Forty-six  Illustrations.     In  one  volume  octavo.     Price       .     ^6.00 

ALLEN   (ALFRE^H.).  F.  C.  S  , 
Lecturer  on  Chemistry  at  the  Sheffield  SchocI  of  Medicine. 

AN  INTRODUCTION  TO  THE  PRACTICE  OF  COMMER- 
CIAL ORGANIC  ANALYSIS.  Being  a  Treatise  on  the  Properties, 
Proximate  Analytical  Examination,  and  Modes  of  Assaying  the  various 
Organic  Chemicals  and  Preparations  employed  in  the  Arts,  Manufac- 
tures, Medicine,  etc.  ;  with  Concise  Methods  for  the  Detection  and 
Determination  of  their  Impurities,  Adulterations,  and  Products  of  De- 
composition. Vol.  I. —  Cyanogen  Compounds,  Alcohols  and  their 
Derivatives,  Phenols,  Acids,  etc.     Price        .         .         .         .         ,$3 -50 

AGNEW  (d.  HAYES),  M.D.. 

Professor  of  Surgery  in  the  University  of  Pennsylvania. 

THE  LACERATIONS  OF  THE  FEMALE  PERINEUM.  AND 
VESICO-VAGINAL  FISTULA,  their  History  and  Treatment,  with 
numerous  Illustrations.      Octavo.      Price  .  .  .  .      $1.50 


ACTON  (WILLIAM),  M.R.C.S.,  etc. 

THE  FUNCTIONS  AND  DISORDERS  OF  THE  REPRODUC- 
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Life,  considered  in  their  Physiological,  Social,  and  Moral  Relations. 
Fourth  American  from  the  Fifth  London  Edition.  Carefully  revised  by 
the  Author,  with  additions.      .......      $2.50 

Mr.  Actou  has  done  good  service  to  society  hy  grappling  manfully  with  sexual  vice,  and 
we  trust  that  others,  whose  jxisition  as  men  of  science  and  teachers  enable  them  to  speak 
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Physician  to  Chelsea  Hospital  for  Diseases  of  Women. 

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Professor  of  Clinical  Medicine  in  the  University  of  Glasgow,  &.c. 
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larged Edition.     Octavo.     Price        .         .         .         .         .         .      $2.50 

BUZZARD'S  CLINICAL  ASPECTS  OF  SYPHILITIC  NER- 
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BASHAM'S  AIDS  TO  THE  DIAGNOSIS  OF  DISEASES  OF 
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BASHAM  ON  DROPSY,  AND  ITS  CONNECTION  WITH 
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With  Sixteen  Plates.      Third  Edition.      Octavo         .        ,.  .      1^4.50 

BARTH  AND  ROGERS  MANUAL  OF  AUSCULTATION 
AND  PERCUSSION.     From  the  Sixth  French  Edition  $1.00 

BRADLEY'S  MANUAL  OF  COMPARATIVE  ANATOMY 
AND  PHYSIOLOGY.     Sixty  Illustrations.     Third  Edition    .      $2.00 

BERNAY'.S  (ALBERT  J.),  Ph.  D. 

Professor  of  Chemistry  at  St.  Thomas's  Hospital. 

N0TP:S  I'OR  STUDhLNTS  IN  CHEMLSTRY.  Compiled  from 
Fowne's  and  other  Manuals.     The  Sixth  Edition.     Cloth         .     $1.25 

BY  SAME  AUTHOR. 

THE  STUDENTS  GUIDE  TO  MEDICAL  CHEMISTRY. 
With  Illustrations.     Preparing. 


8 

BEALE  (LIONEL  s.),  M.D. 

DISEASE  GERMS:   AND  ON   THE  TREATMENT   OF   DIS-  • 
EASES  CAUSED  BY  THEM. 

Part      L— SUPPOSED  NATURE  OF  DISEASE  GERMS. 
Part    II.  — REAL  NATURE  OF  DISEASE  GERMS. 
Part  III.  — THE  DESTRUCTION  OF  DISEASE  GERMS. 

Second  Edition,  much  enlarged,  with  Twenty-eight  full-page  Plates, 
containing  117  Illustrations,  many  of  them  colored.     Demy  Octavo. 

Price ^4-oo 

LIFE  THEORIES  AND  RELIGIOUS  THOUGHT  ON  LIFE 
AND  VITAL  ACTION  IN  HEALTH  AND  DISEASE.  With 
Plates.     Price ^2.25 

SAME  AUTHOR. 

BIOPLASM.  A  Contribution  to  the  Physiology  of  Life,  or  an  Intro- 
duction to  the  Study  of  Physiology  and  Medicine,  for  Students.  With 
Numerous  Illustrations.     Price ^2.25 

This  volume  is  intended  as  a  Text-Book  for  Students  of  Physiology,  explaining  the  nature 
of  some  of  the  most  important  changes  which  are  characteristic  of  and  peculiar  to  living 
beings. 

PROTOPLASM,  OR  MATTER  AND  LIFE.  Third  Edition,  very 
much  Enlarged.  Nearly  350  pages.  Sixteen  Colored  Plates.  One 
volume.     Price      .........      $3-oo 

Part  I.  DISSENTIENT.      Part  II.  DEMONSTRATIVE.     Part  III.  SUGGESTIVE. 

HOW  TO  WORK  WITH  THE  MICROSCOPE.     Fifth  Edition, 

containing  400  Illustrations,  many  of  them  colored.     Octavo.      $7-5° 

This  work  is  a  complete  manual  of  microscopical  manipulation,  and  contains  a  full  descrip- 
tion of  many  new  processes  of  investigation,  witli  directions  for  examining  objects  under  the 
higliest  powers,  and  for  taking  photogra^jhs  of  microscopic  objects. 

ON  KIDNEY  DISEASES,  URINARY  DEPOSITS,  AND  CAL- 
CULOUS DISORDERS.  Including  the  Symptoms,  Diagnosis,  and 
Treatment  of  Urinary  Diseases.  With  full  Directions  for  the  Chemical 
and  Microscopical  Analysis  of  the  Urine  in  Health  and  Disease.  The 
Third  Edition.  Seventy  Plates,  415  figures,  copied  from  Nature. 
Octavo.     Price .     ^10.00 

THE  USE  OF  THE  MICROSCOPE  IN  PRACTICAL  MEDL 
CINE.  For  Students  and  Practitioners,  with  full  directions  for  exam- 
ining the  various  secretions,  &c.,  in  the  Microscope.  Fourth  Edition. 
500  Illustrations.     Octavo.       Much  enlarged.     Price       .         .     |7-5o 

BLOXAM  (c.  L.), 

Professor  of  Chemistry  in  King's  College,  London. 

CHEMISTRY,  INORGANIC  AND  ORGANIC.  With  Experi- 
ments and  a  Comparison  of  Equivalent  and  Molecular  Formulae.  With 
276  Engravings  on  Wood.  Third  London  Edition,  revised.  Octavo. 
Price,  in  cloth,  $4.00;   leather,        ......      $5-oo 

SAME  AUTHOR. 
LABORATORY    TEACHING;     OR    PROGRESSIVE    EXER- 
CISES   IN   PRACTICAL    CHEMISTRY.      Fourth   Edition.      With 
Eighty-nine  Engravings.      Crown  Octavo.     Price    .         .         .     ^1.75 


BENNETT  (j.  henry),  M.  D. 

NUTRITION  IN  HEALTH  AND  DISEASE.  A  Contribution 
to  Hygiene  and  to  Clinical  Medicine.  Third  Edition,  Revised  and 
Enlarged.     Octavo.     Cloth.     Price $2.50 

BY  SAME  AUTHOR. 
THE  TREATMENT  OF    PULMONARY  CONSUMPTION   BY 
HYGIENE,  CLIMATE,  AND  MEDICINE.     With  an  Appendix  on 
the  Sanitaria  of  the  United  States,  Switzerland,  and  the  Balearic  Isl- 
ands.    The  Third  Edition,  much  Enlarged.     Octavo.     Price    .   $2.50 

BUCKNILL(joHN  CHARLES),  M.D.,  &  TUKE  (daniel  h.),M.D. 

A  MANUAL  OF  PSYCHOLOGICAL  MEDICINE:  containing  the 
Lunacy  Laws,  the  Nosology,  CEtiology,  Statistics,  Description,  Diagno- 
sis, Pathology  (including  Morbid  Histology),  and  Treatment  of  Insanity. 
Fourth  Edition,  much  enlarged,  with  Twelve  Lithographic  Plates,  and 
numerous  Illustrations.     Octavo.     Price  ....     ^8.00 

This  edition  will  contain  a  number  of  pages  of  additional  matter,  and,  in  consequence  of 
recent  advances  in  Psychological  Medicine,  several  chapters  will  be  rewritten,  bringing  the 
Classification,  Pathology,  and  Treatment  of  Insanity  up  to  the  present  time. 

BURNETT  (CHARLES  h.),  M.  D., 

Aurist  to  {he  Presbyterian  Hospital,  &c, 

HEARING,  AND  HOW  TO  KEEP  IT.  (Vol.  I.,  American  Health 
Primers.)     With  Illustrations.      Cloth.      Price      .  .  .  $0.50 

BIDDLE  "(^S^B.),  M.  D., 

Professor  of  Materia  Medica  and  Therapeutics  in  the  Jefferson  Medical  College,  Phiiadelphia,  &.c. 

MATERIA  MEDICA,  FOR  THE  USE  OF  STUDENTS.  With 
Illustrations.      Eighth  Edition,  Revised  and  Enlarged.     Price     $4.00 

This  new  and  thoroughly  revised  edition  of  Professor  Biddle's  work  has  incorporated  in 
it  all  the  improvements  as  adopted  by  the  New  United  States  Pharmacopoeia  just  issued.  It 
is  designed  to  present  the  leading  facts  and  principles  usually  comprised  under  this  head  as 
set  forth  by  the  standard  authorities,  and  to  fill  a  vacuum  which  seems  to  exist  in  the  want 
of  an  elementary  work  on  the  surjject.  Tho  larger  works  usually  recommended  as  text-books 
in  our  Medical  schools  are  too  voluminous  for  convenient  use.  This  will  be  found  to  contaia, 
in  a  condensed  form,  all  that  is  most  valuable,  and  will  supply  students  with  a  reliable  guide 
to  the  course  of  lectures  on  Materia  Medica  as  delivered  at  the  various  Medical  schools  in 
the  United  States. 

BALFOUrTgTw.),  M.D., 

Physician  to  the  Royal  Infirmary,  Edinburgh;  Lecturer  on  Clinical  Medicine,  &c. 

CLINICAL  LECTURP:S  on  diseases  of  the  heart  AND 
AORTA.     With  Illustrations.     Octavo.     Price       .         .         .     $4.00 

BYFORD  (v^nryTA.M.,  M.D., 

Professor  of  Obstetrics  and  Diseases  of  Women  and  Children  in  the  Chicago  Medical  College,  &c, 

practice  of  medicine  AND  SURGERY.  Applied  to  the 
Diseases  and  Accidents  incident  to  Women.  Second  Edition,  Revised 
and  Enlarged.     Octavo.     Price 

SAME  AUTHOR. 

ON  THE  CHRONIC  INFLAMMATION  AND  DISPLACEMEN'I 

OF  THE   UNIMPRKC;NATED  uterus,     a  New,   Enlarged,  and 

Thoroughly  Revised  P>lition,  with  Numerous  Illustrations.    8vo.     $2.50 

Dr.  Ryford  writ^^s  the  exact  present  state  of  medical  knowledge  on  the  subjects  presented  ; 

and  does  this  so  clearly,  ko  concisely,  so  truthfully,  and  so  completely,  that  his  book  on  the 

ut<;ruH  will  always  meet  the  approval  of  the  profession,  and  be  everywhere  regarded  as  a 

[xtpular  standard  work.  — Jiujf'ulo  Medical  and  Hur'jicul  Journal. 


10 

BLACK    (d.  CAMPBELL),    M.  D., 
L.  R.  C.  S.  Edinburgh,  Member  of  the  General  Council  of  the  University  of  Glasgow-,  Slc,  &c, 

THE  FUNCTIONAL  DISEASES  OF  THE  RENAL,  URINARY, 

and  Reproductive  Organs,  with  a  General  View  of  Urinary  Pathology. 

Price     .         .         .         .         .         .         .         .         .         •         .      $2.00 

The  style  of  the  author  is  clear,  easy,  and  agreeable,  .  .  .  his  work  is  a  valuable  contri- 
bution to  medical  science,  and  being  penned  in  that  disposition  of  unprejudiced  philosophical 
inquiry  which  should  always  guide  a  true  physician,  admirably  embodies  the  spirit  of  its 
opening  quotation  from  Professor  Huxley.  —  Pkilada.  3Ied.  Times. 

BY  SAME  AUTHOR. 
LECTURES   ON   BRIGHT'S    DISEASE  OF  THE   KIDNEYS. 

Delivered  at  the  Royal  Infirmary  of  Glasgow.  With  20  Illustrations, 
engraved  on  Wood.     One  volume,  octavo,  in  Cloth.     Price     .     $1.50 

BENTLEY  and  TRIMEN'S 

MEDICINAL    PLANTS.      A  New  Illustrated  Work,  Complete  in 

Forty -two  Parts.      Eight  Colored  Plates  in  each  Part.      Price,  each, 

^2.00  j  or  in  Four  Vols.,  One-Half  Morocco,  Gilt  Heads      .      ^90.00 

This  work  includes  full  botanical  descriptions,  and  an  account  of  the  properties  and  uses 
of  the  principal  plants  employed  in  medicine,  especial  attention  being  jsaid  to  those  which 
are  ofiicinal  in  the  British  and  United  States  Pharinacopffiias.  The  plants  which  supply 
food  and  substances  required  by  the  sick  and  convalescent  will  be  also  included.  Each  spe- 
cies will  be  illustrated  by  a  colored  plate  drawn  from  nature. 

BEASLEY  (henry). 

THE     BOOK    OF     PRESCRIPTIONS.       Containing   over   3000 

Prescriptions,  collected  from  the  Practice  of  the  most  Eminent  Physi- 
cians and  Surgeons — English,  French,  and  American  ;  comprising  also 
a  Compendious  History  of  the  Materia  Medica,  Lists  of  the  Doses  of  all 
Officinal  and  Established  Preparations,  and  an  Index  of  Diseases  and 
their  Remedies.     Fifth  Edition,  Revised  and  Enlarged.     Price     ^2.25 

BY  SAME  AUTHOR. 

THE  POCKET  FORMULARY:  A  Synopsis  of  the  British  and 
Foreign  Pharmacopoeias.     Tenth  Revised  Edition.     Price       .     ^2.25 

THE  DRUGGIST'S  GENERAL  RECEIPT  BOOK  and  VETERI- 
NARY FORMULARY.     Eighth  Edition.     Just  Ready.     Price,  ^2.25 

BIRCH  (s,  B.),  M.  D., 

Member  of  the  Royal  College  of  Physicians,  &Ci 
CONSTIPATED  BOWELS ;  the  Various  Causes  and  the  Different 
Means  of  Cure. 

BRAUNE— BELLAMY. 

AN  ATLAS  OF  TOPOGRAPHICAL  ANATOMY.  After  Plane 
Sections  of  Frozen  Bodies,  containing  Thirty-four  Full-page  Photo- 
graphic Plates  and  numerous  other  Illustrations  on  Wood.  By  Wilhelm 
Braune,  Professor  of  Anatomy  in  the  University  of  Leipzig.  Trans- 
lated and  Edited  by  Edward  Bellamy,  F.  R.  C.  S.,  Senior  Assistant  Sur- 
geon to,  and  Lecturer  on  Anatomy  and  Teacher  of  Operative  Surgery 
at,  the  Charing  Cross  Hospital,  London.  A  large  quarto  volume. 
Price  in  cloth,  ^12.00  ;  half  morocco,    .....     ^14.00 


11  "■ 

COHEN   (i.  soLis),  M.D. 

Lecturer  on  Laryngoscopy  and  Diseases  of  the  Throat  and  Chest  in  Jefferson  Medical  ColleEre. 

ON  INHALATION.     ITS  THERAPEUTICS  AND  PRACTICE 

Including  a  Description  of  the  Apparatus  employed,  &c.      With  Cases 
and  Illustrations.      A  New  Enlarged  Edition.     Price        .         .     $2.50 

SAME  AUTHOR. 
CROUP.     In  its  Relations  to  Tracheotomy.     Price         .         .    $l.oc 

CARSON  (JOSEPH),  M.D., 

Professor  of  Materia  Medica  and  Pharmacy  in  the  University. 

A  HISTORY  OF  THE  MEDICAL  DEPARTMENT  OF  THE 
UNIVERSITY  OF  PENNSYLVANIA,  from  its  Foundation  in  1765: 
with  Sketches  of  Deceased  Professors,  &c.       .         .         .         .      ^2.00 

CHARTERIsTmTthew),  M.  D., 

Member  of  Hospital  Staff  and  Professor  in  University  of  Glasgow, 

STUDENTS'  HAND-BOOK  OF  THE  PRACTICE  OF  MEDI- 
CINE.     With  Microscopic  and  other  Illustrations.      Price         .      $2.00 

This  book  forms  oue  volume  of  the  Students'  Guide  Series,  or  Text-Books,  now  ia  counse 
of  publicatioa. 

CARPENTER  (w.  b.),  M.D.,  F.R.S. 
THE   MICROSCOPE  AND    ITS    REVELATIONS.      The   s.xth 
London  Edition,  Revised  and  Enlarged,  with  more  than  500  Illustra- 
tions.   ........... 

CORR  (l.  h.),  M.D. 

OBSTETRIC    CATECHISM,  or  Obstetrics   reduced  to  Questions 

and  Answers.      With  Numerous  Illustrations.      Price         .  .      ^2.00 

CHAVASSE  (p.  henry),  F.R.C.S., 

Author  of  Advice  to  a  Wife,  Advice  to  a  Mother,  &c. 

APHORISMS  ON  THE  MENTAL  CULTURE  AND  TRAIN- 
ING OF  A  CHILD,  and  on  various  other  subjects  relating  to  Health 
and  Happiness.     Addressed  to  Parents.     Price         .  .         .      ^i.oo 

Dr.  Chavasse's  works  have  been  very  favorably  received  and  had  a  large  circulation,  the 
value  of  his  advice  to  WIVES  and  MOTHERS  "having thus  been  very  generally  recognize<l. 
This  book  is  a  sequel  or  companion  to  them,  and  it  will  be  found  both  valuable  and  ini])or(anl 
U>  all  who  have  the  care  of  families,  and  wlio  want  to  bring  up  their  diildren  to  become  useful 
men  aufl  women.     It  is  full  of  fresh  thoughts  and  graceful  illustrations. 

CLARKE  (w.fairlie),  M.D., 

Assistant  Surgeon  to  Charing  Cross  Hospital. 

CLARKE'S   TREATISE  ON  DISEASES   OF  THE  TONGUE. 

With  Lithograjihic  and  Wood-cut  Illustrations.     Octavo.     Price  ^4.50 

It  contains  The  Anatomy  and  Physiology  of  the  Tongue,  Importance  of  its  Minute  Exam- 
ination, [tH  Congenital  Defects,  Atroi)hy,  "Hypertrophy,  Parasitic  Diseases,  Intiammation, 
Byphilis  and  ita  effecte,  Various  Tumors  to  which  it  is  subject.  Accidents,  Injuries,  <fec.,  <tc. 

COOPER  (.s.). 

A  DICTIONARY  OF   PRACTICAL   SURGERY  AND   ENGY- 

CL0P^:DIA   of    SURC;ICAL    science.     New  Edition,  brought 

down  to  the  present  time.     By  Samukl  A.  Lane,  F.R.C.S.,  assisted  by 

other  eminent  Surgeons.     In  two  vols.,  of  over  1000  pages  each.    ;^  1-2. 00 


CLAY  (CHARLES),  M.  D. 

Fellow  of  the  London  Obstetrical  Society,  &c. 

THE  COMPLETE  HAND-BOOK  OF  OBSTETRIC  SURGERY, 

or,  Short  Rules  of  Practice  in  Every  Emergency,  from  the  Simplest  to 
the  most  Formidable  Operations  in  the  Practice  of  Surgery.  First 
American  from  the  Third  London  Edition.  With  numerous  Illustra- 
tions.    In  one  volume.  ^2.00 

CHAMBERS  (thomas  k.),  M.  D., 

LECTURES,  CHIEFLY  CLINICAL.  Illustrative  of  a  Restorative 
System  of  Medicine. 

CORMACK  (sir  john  ^J^^K.  B.,  F.  R.  S.  E.,  M.  D. 

Edinburgh  and  Paris,  Fellow  Royal  College  of  Physicians,  Physician  to  the  Hertford  British  Hospital,  Paris,  &c. 

CLINICAL  STUDIES,  Illustrated  by  Cases  observed  in  Hospital  and 
Private  Practice.    With  Illustrative  Plates.    2  Volumes.    Octavo.      ^5.00 

COBBOLD  (t.  spencer),  M.  D.,  F.  R.  S. 

PARASITES :  A  Treatise  on  the  Entozoa  of  Man  and  Animals ; 
including  some  Account  of  the  Ectozoa.  With  85  Engravings.  Oc- 
tavo.    Price  ..........     I5.00 

CLEAVELAND  (c.  h.),  M.D., 

Member  of  the  American  Medical  Association,  &.c, 

A  PRONOUNCING  MEDICAL  LEXICON.  Containing  the  Cor- 
rect Pronunciation  and  Definition  of  Terms  used  in  Medicine  and  the 
Collateral  Sciences.     Improved  Edition,  Cloth,    75  cts.  ;  Tucks,  $1.00 

This  work  is  not  only  a  Lexicon  of  all  the  words  in  common  use  in  Medicine,  but  it  is 
also  a  Pronouncing  Dictionary,  a  feature  of  great  value  to  Medical  Students.  To  the  Dis- 
penser it  will  prove  an  excellent  aid,  and  also  to  the  Pharmaceutical  Student.  It  has  received 
strong  commendation  both  from  the  Medical  Press  and  from  the  j)rofession. 

COLES  (oakley),  D.D.S. 

Dental  Surgeon  to  the  Hospital  for  Diseases  of  the  Throat,  Slc. 

A  MANUAL  OF  DENTAL  MECHANICS.  Containing  much 
information  of  a  Practical  Nature  for  Practitioners  and  Students. 

INCLUDING     . 

.  The  Preparation  of  the  Mouth  for  Artificial  Teeth,  on  Taking  Impressions,  Various 

Modes  of  Applying  Heat  in  the  Laboratory,  Casting  in  Plaster  of  Paris  and  Metal, 
Precious  Metals  used  in  Dentistry,  Making  Gold  Plates,  Various  Forms  of  Porcelain 
used  in  Mechanical  Dentistry,  Pivot  Teeth,  Choosing  and  Adjusting  Mineral  Teeth,  the 
Vulcanite  Base,  the  Celluloid  Base,  Treatment  of  Deformities  of  the  Mouth,  Eeceipts 
for  Making  Gold  Plate  and  Solder,  etc.,  etc. 
With  140  Illustrations.     Price         ......     $2.00 

SAME  AUTHOR. 

ON  DEFORMITIES  OF  THE  MOUTH,  CONGENITAL  AND 
ACQUIRED,  with  their  Mechanical  Treatment.  Second  Edition,  Re- 
vised and  Enlarged.     With  Illustrations.     Price,     . 

DOMVILLE  (EDWARD  J.),  M.  D. 

A  MANUAL  FOR  HOSPITAL  NURSES  and  Others  engaged  in 
Attending  the  Sick.     i2mo.     Price         .         .         .         .         .     ^i.oo 


13 

CLARK  (f.  le  gros),  F.  R.  S., 

Senior  Surgeon  to  St.  Thomas's  Hospital. 

OUTLINES  OF  SURGERY  AND  SURGICAL  PATHOLOGY, 
including  the  Diagnosis  and  Treatment  of  Obscure  and  Urgent  Cases, 
and  the  Surgical  Anatomy  of  some  Important  Structures  and  Regions. 
Assisted  by  W.  W.  Wagstaffe,  F.  R.  C.  S.,  Resident  Assistant-Surgeon 
of,  and  Joint  Lecturer  on  Anatomy  at,  St.  Thomas's  Hospital.  Second 
Edition,  Revised  and  Enlarged.      Price  .         .         .         .     ^2.00 

COTTLE  (e.  wyndham),  M.  A..  F.  R.  C.  S.,  &c. 
THE  HAIR  IN  HEALTH  AND  DISEASE.     Partly  from  Notes 
by  the  late  George  Navler,  F.  R.  C.  S.,  Surgeon  to  the  Hospital  for 
Diseases  of  the  Skin,  &c.      i8mo.      Cloth.     Price        .         .         $o-75 

CURLING  (t.  b.),  F.R.S., 

Consulting  Surgeon  to  the  London  Hospital,  &,c. 

A  PRACTICAL  TREATISE  ON  THE  DISEASES  OF  THE 
TESTIS  AND  OF  THE    SPERMATIC    CORD  AND  SCROTUM. 

Fourth  Revised  and  Enlarged  Edition.     Octavo.     Price.         .     $5-5o 

BY  SAME  AUTHOR. 

OBSERVATIONS  ON  DISEASES  OF  THE   RECTUM.  With 

Illustrations.     Fourth  Edition,  Revised  and  Enlarged.    Octavo.  Cloth. 

Price .         .         .  $2.75 

CAZEAUX  (p.).  M.  D., 

Adjunct  Professor  of  the  Faculty  of  Medicine,  Paris,  etc. 

A  THEORETICAL  AND  PRACTICAL  TREATISE  ON  MIDWIFERY, 
including  the  Diseases  of  Pregnancy  and  Parturition.  Translated  from 
the  Seventh  French  Edition,  ReA^sed,  Greatly  Enlarged,  and  Improved, 
by  S.  Tarnier,  Clinical  Chief  of  the  Lying-in  Hospital,  Paris,  etc., 
with  numerous  Lithographic  and  other  Illustrations.  Price,  in  Cloth, 
$6.00;   in  Leather         ........      $7-oo 

M.  Cazeaux's  Great  Work  on  Obstetrics  has  become  classical  in  its  character,  and  almost 
an  Encyclopie<iia  in  its  fulness.  Written  expressly  for  the  use  of  students  of  medicine,  its 
teachinsjs  are  ])lain  and  explicit,  presenting  a  condensed  summary  of  the  leading  principles 
established  by  the  masters  of  the  obstetric  art,  and  such  clear,  practical  directions  for  the 
management  of  the  pregnant,  parturient,  and  ))uerperal  states,  as  have  been  sanctioned  by 
the  moat  authoritative  practitioners,  and  confirmed  by  the  author's  own  experience. 

DOBELL  (HORACE),  M.D., 

Senior  Physician  to  the  Hospital. 

WINTER  COUGH  (CATARRH,  BRONCHITIS,  EMPHYSEMA, 
ASTHMA).  Lectures  Delivered  at  the  Royal  Hospital  for  Diseases  of 
the  Chest.  The  Third  Enlarged  Edition,  with  Colored  Plates.  Octavo. 
Price $3.50 

BY  SAME  AUTHOR. 

ON  LO.SS  OF  WEIGHT,  BLOOD-SPITTING,  AND  LUNG 
DISfc^ASE.  With  a  Colored  Frontispiece  of  the  Lung,  a  Tabular  Map, 
&c.,  &c.     Octavo.     Cloth.     Price          .         .         .         .         •     ?53-25 


14 
DIXON  (jAMEs),  F.R.  CS. 

Surgeon  to  the  Royal  London  Ophtha'mic  Hospital,  ic. 

A  GUIDE  TO  THE  PRACTICAL  STUDY  OF  DISEASES  OF 

THE  EYE,  with  an  Outline  of  their  Medical  and  Operative  Treatment, 

with  Test  Types  and  Illustrations.     Third  Edition,  thoroughly  Revised, 

and  a  great  portion  Rewritten.     Price     .....     ^2.00 

Mr.  Dixon's  book  is  essentially  a  practical  one,  written  by  an  observant  author,  who  brings 
to  has  special  subject  a  sound  knowledge  of  general  Medicine  and  Unrgery. —Uubiin  Quarteriy 

DILLNBERGER  (dr.  emil). 

A  HANDY-BOOK  OF  THE  TREATMENT  OF  WOMEN  AND 

CHILDREN'S  DISEASES,  according  to  the  Vienna  Medical  School. 

Part  I.  The  Diseases  of  Women.      Part  II.   The  Diseases  of  Children. 

Translated    from   the    Second    German  Edition,  by  P.   Nicol,  M.  D. 

Price ^1-5° 

Many  practitioners  will  be  glad  to  possess  this  little  manual,  which  gives  a  large  mass 
(A  practical  hints  on  the  treatment  of  diseases  which  probably  make  up  tlie  larger  half  oi 
every-day  practice.  The  translation  is  well  made,  and  exjilanations  of  reference  to  German 
medicinal  preparations  are  given  with  proper  fulness.  —  The  Practitioner. 

DUNGLISON  (RICHARD  j.),  M.  D. 

THE    PRACTITIONER'S  REFERENCE    BOOK.      Containing 

Therapeutic  and   Practical  Hints,  Dietetic  Rules  and  Precepts,   and 

other  General  Information  Useful  to  the  Physician,  Pharmacist,  and 

Student.     Octavo.     Cloth.  Second  Edition.     Price     .         .         $2fS^ 

DUCHENNE  (dr.  g.  b.). 
LOCALIZED    ELECTRIZATION    AND    ITS    APPLICATION 
TO  PATPIOLOGY  AND    THERAPEUTICS.     Translated  by  Her- 
bert TiBBiTS,  M.D.     With  Ninety-two  Illustrations.     Price     .     $3.00 
Duchenne's  great  work  is  not  only  a  well-nigh  exhaustive  treatise  on  the  medical  uses  of 
Electricity,  but  it  is  also  an  elaborate  exposition  of  the  diflferent  diseases  in  which  Electric- 
ity has  proved  to  be  of  value  as  a  therapeutic  and  diagnostic  agent. 

Part  II.,  illustrated  by  chromo-lithographs  and  numerous  wood-cuts,  is  preparing. 

DURKEE  (siLAs),  M.D., 

Fellow  of  the  Massachusetts  Medical  Society,  &c, 

GONORRHCEA  AND  SYPHILIS.  The  Sixth  Edition,  Revised 
and  Enlarged,  with  Portraits  and  Eight  Colored  Illustrations.  Octavo. 
Price ^3-5° 

Dr.  Durkee 
thorough  hon 

ner  in  which  the  facts  are  cited,  the  clever  way 

in,  the  lucidity  of  the  reasoning,  and  the  care  with  which  the  therapeutics  ot  venereal  com- 
plaints are  treated. —  Lancet. 

DRUITT  (ROBERT),  F.R.C.S. 
THE  SURGEON'S  VADE-MECUM.     A  Manual  of  Modern  Sur- 
gery.    The  Eleventh  Revised  and   Enlarged  Edition,  with  369   lUus- 
trations.      Price     .  .         .  ■         •         •         •  •         •     $S-°° 


15 
DALBY  (w.  B.),  F.  R.  C.  S., 

Aural  Surgeon  to  St.  George's  Hospital. 

LECTURES  ON  THE  DISEASES  AND  INJURIES  OF  THE 
EAR.  Delivered  at  St.  George's  Hospital.  With  Illustrations. 
Price ^1-50 

We  eordiallv  recommend  this  admirable  volume  hy  Mr.  Dalby  as  a  trustworlliy  tjiiide  in 
the  treatment  of  tite  ati'eetions  of  the  ear.  The  bookis  moderate  in  price,  beautifully  illus- 
trated by  wood  cuts,  and  got  up  in  the  best  style.  —  Glungoiv  Medical  Journal. 

DAY  (WILLIAM  henry).  M.  D., 

Physician  to  the  Samaritan  Hospital  for  Women  and  Children,  die. 

HEADACHES,  THEIR  NATURE.  CAUSES,  AND  TREAT- 
MENT.    Third    Edition.       121110.     Cloth.     Price  .         .     $2.00 

ELLIS  (EDWARD).  M.  D., 
Physician  to  the  Victoria  Hospital  for  Sick  Children,  &c. 

A  PRACTICAL  MANUAL  OF  THE  DISEASES  OF  CHIL- 
DREN, with  a  Formulary.  Third  Enlarged  Edition,  Revised  and 
Improved.     One  volume     ....... 

The  AlTTHOR,  in  issuing  this  new  edition  of  his  book,  says  :  "  I  have  very  carefully  revised 
each  chai)ter,  adding  several  new  sections,  and  making  "considerable  additions  where  the 
subjects  seemed  to  require  fuller  treatment,  without,  however,  sacrificing  conciseues.s  or 
uaduly  increasing  the  bulk  of  the  volume." 

FENWICK   (SAMUEL). 

OUTLINES  OF  THE  PRACTICE  OF  MEDICINE.    With  special 

reference  to  the  Prognosis  and  Treatment  of  Disease.     With  Formula 
and  Illustrations.     Large  i2mo.     Price ^2.00 

FOTHERGILL  (j.  milner),  M.  D.. 

Assistant  Physician  to  City  of  London  Hospital  for  Diseases  of  the  Chest,  die. 

THE   HEART,  ITS   DISEASES  AND   THEIR   TREATMENT, 

including  the  Gouty  Heart.      Second  Edition,  Entirely  Rewritten  and 
Enlarged,   with  Two  Full-Page   Lithographic    Plates   and  Forty  other 

Illustrations.      Octavo.      Price ^3-5° 

"  Dr.  FotherKill's  remarks  on  rest,  on  j>roper  blood  nutrition  in  Heart  Disease,  in  the 
treatment  of  Se<iuela;  of  it,  and  on  the  action  of  special  medicines,  all  indicate  that  in  study- 
ing the  i)athology  of  Heart  Disease,  he  has  earnestly  kept  in  view  the  best  means  of  mitigat- 
ing sufl'ering  and  of  prolonging  life."  —  Lancet. 

FOX   (CORNELIUS  B.),   M.  0. 
SANITARY  EXAMINATIONS  of  Water,  Air,  and  Food.     94  En- 
gravings.     8vo.      Price         .  .         .         .         .  .         •        ^4.00 

FOX  (TiLiiUHY),  M.  D..  F.  R.  C.  P. 

Physician  to  the  Department  for  Skin  Diseases  in  University  College  Hosoital. 

ATLAS  OV  SKIN  DISEASE.S.  Consi.sting  of  a  Series  of  Colored 
Iliii^trations,  in  Monthly  Parts,  togetiier  witii  Descri^jtive  Text  and 
Notes  ui>on  Treatment  ;  each  Part  containing  Four  Plates,  reproduced  by 
Chromo-Eithograpliy  from  the  work  of  Willan  &  Pateman,  or  taken  from 
Original  Sources.  Now  Complete  in  18  Parts.  Price,  per  Part,  $2.00  ; 
or  in  one  large  Folio  volume,  bound  in  cloth.     Price     .         .     ;^3o.oo 


16 

FENNER  (c.  s.),  M.  D.,  &c. 

VISION:  ITS  OPTICAL  DEFECTS,  and  the  Adaptation  of  Spec- 
tacles ;  embracing  Physical  Optics,  Physiological  Optics,  Errors  of  Re- 
fraction and  Defects  of  Accommodation,  or  Optical  Defects  of  the  Eye. 
With  74  Illustrations.  Selections  from  the  Test  Types  of  Jaeger  and 
Snellen,  etc.     Octavo.      Price         .         .         .         .         .         -     ^3-5° 

FOSTER   (BALTHAZAR),  M.  D., 

Professor  of  Medicine  in  Queen's  College. 

LECTURES  AND  ESSAYS  ON  CLINICAL  MEDICINE.  Re- 
vised and  Enlarged  by  the  Author.  With  Engravings.  Octavo. 
Price     ......         =         .•••     $3-°° 

FRANKLAND  (e.),  M.  D.,  F.  R.  S.,  &c. 

HOW  TO  TEACH  CHEMISTRY,  being  the  substance  of  Six 
Lectures  to  Science  Teachers.  Reported,  with  the  Author's  sanction, 
by  G.  George  Chaloner,  F.  C.  S.,  8z:c.     With  Illustrations         .     ^1.25 

FULTON  (j.),  M.  D., 

Professor  of  Physiology,  Trinity  Medical  College,  TorontOi 

A  TEXT-BOOK  OF  PHYSIOLOGY.  Second  Edition,  Revised 
and  Enlarged.     With  numerous  Illusti-ations.     Octavo.     Price      ^4.00 

FLINT  (AUSTIN),  M.D., 

Professor  of  the  Principles  and  Practice  of  Medicine,  &c.,  Bellevue  Hospital  College,  New  Ycrk. 

CLINICAL  REPORTS  ON  CONTINUED  FEVER.  Based  on 
an  Analysis  of  One  Hundred  and  Sixty-four  Cases,  with  Remarks  on 
the  Management  of  Continued  Fever;  the  Identity  of  Typhus  and 
Typhoid  Fever;  Diagnosis,  &c.,  &c.     Octavo.     Price    .  .     ^2.00 

GANT    (FREDERICK  J.),  F.  R.  C.  S., 
Assisted  by  Drs.  Morrell   Mackenzie,  Barnes,  Erasmus  Wilson,  and  other  Specialists!' 

THE    SCIENCE    AND    PRACTICE    OF    SURGERY.     Second 

Edition.    1700  Pages.    1000  Illustrations.   2  Vols.    Price,  cloth,  ^11.00  ; 
sheep  .         .         .  .  .  .         .  .         .  .  .     ^13.00 

DISEASES  OF  THE  BLADDER,  PROSTATE  GLAND,  AND 
URETHRA,  including  a  Practical  View  of  Urinary  Diseases,  Deposits, 
and  Calculi.  Fourth  Edition,  Revised  and  Enlarged.  With  New  Il- 
lustrations.    Now  Ready.     Price    ......     $3.00 

GODLEE  (r.  J.),  M.D., 

Assistant-Surgeon  University  College  Hospitali 

AN  ATLAS  OF  HUMAN  ANATOMY.  Illustrating  the  Anatomy 
of  the  Human  Body,  in  a  Series  of  Dissections.  Accompanied  by 
References  and  an  Explanatory  Text.  To  be  completed  in  Twelve  or 
Thirteen  Bi-monthly  Parts,  Folio  Size,  each  Part  containing  Four  large 
Colored  Plates,  or  Eight  Figures.  Ten  Parts  Now  Ready.  Price  per 
Part ^2.50 


17 
GROSS  (SAMUEL  D.),  M.  D., 

Professor  of  Surgery  in  the  Jefferson  Medical  College,  Philadelphia,  etc. 

AMERICAN  MEDICAL  BIOGRAPHY  OF  THE  NINETEENTH 

CENTURY.  With  a  Portrait  of  Benjamin  Rush,  M.D.    Octavo.    $3.50 

GREENHOW  (e.  headlam).  M.  D., 

Fellow  of  the  Royal  Collego  of  Physicians,  etc. 

ON  CHRONIC  BRONCHITIS,  Especially  as  Connected  with  Gout. 
Emphysema,  aijd  Diseases  of  the  Heart.     Price      .         .         .     $1.50 

ADDISON'S  DISEASE.  Illustrated  by  numerous  Cases  and  5 
full-page  Colored  Engravings.      Price       .  .  .  .  .     I3.00 

GOWERS  (w.  R.),  M.  D.,  F.  R.  C.  P., 

Assistant  Professor  of  Clinical  Medicine  in  University  College. 

A  MANUAL  AND  ATLAS  OF  MEDICAL  OPHTHALMO- 
SCOPY. With  16  Colored,  Autotype,  and  Lithographic  Plates,  and 
26  Woodcuts,  comprising  112  original  Illustrations  of  the  Changes  in 
the  Eye  in  Diseases  of  the  Brain,  Kidneys,  etc.     Octavo.   .     .     $6.00 

GALLABIN  (alfred  lewis),  M.  D., 

Assistant  Obstetric  Physician  and  Joint  Lecturer  on  Midwifery,  Guy's  Hospital,  &c. 

THE  STUDENT'S  GUIDE  TO  THE  DISEASES  OF  WOMEN. 

With  Numerous  Illustrations.      i2mo.      Cloth.      Price     .  .     ^2.00 

HIGGINS  (chX^s),  F.  R.  C.  S., 

Ophthalmic  Surgeon,  Guy's  Hospital,  &c. 

HINTS  ON  OPHTHALMIC  OUT-PATIENT  PRACTICE.  Sec- 
ond Edition.      i6mo.     Cloth.     Price         ....         60  cts. 

HUNTErTcharles). 
MECHANICAL  DENTISTRY.     A  Practical  Treatise  on  the  Con- 
struction of  the  Various  Kinds  of  Artificial  Dentures,  with  Formula, 
Receipts,  &c.      100  Illustrations.      Price  ....     $2.. 2^ 

HEATH   (CHRISTOPHER),  F.  R.  C.  S., 

Surgeon  to  University  College  Hospital  and  Holme  Professor  of  Clinical  Surgery  in  University  College, 

OPERATIVE  SURGERY.  Elegantly  Illustrated  by  20  Large  Col- 
ored Plates,  Imperial  Quarto  Size,  each  Plate  containing  several  Fig- 
ures, drawn  from  Nature  by  M.  Leveille',  of  Paris,  and  Colored  by  hand 
under  his  direction.  (Complete  in  Five  Quarterly  Parts.  Price,  per  Part, 
$2.50;  or  in  one  volume,  handsomely  bound  ui  cloth.     Price     $14.00 

HEWITT  (grah  y),  M.  D., 

Physician  to  the  British  Lying-in  Hospital,  and  Lecturer  on  Diseases  of  Women  and  Children,  &c, 

THE  DIAGNOSIS,  PATHOLOGY,  AND  TREATMICNT  OF 
DISEA.SES  OF  WOMEN,  including  the  Diagnosis  of  Pregnancy. 
Founded  on  a  Course  of  Lectures  delivered  at  St.  Mary's  Hospital 
Medical  School.  The  Third  Edition,  Revised  and  Enlarged,  with 
new  Illustrations.     Octavo.     Price  in  Cloth         .         .         .         j;4.oo 

"         Leather     .         .  .  5.00 

Tliis  new  edition  of  Dr.  Ilcwitt'.sbook  has  been  bo  much  modificil,  that  it  may  bo  considered 
subHtiintiuliy  anf;w  bv^k  ;  very  much  of  the  matter  has  been  entirely  rewritten,  and  tliewliole 
■work  ha.H  been  rearrancfcd  in  hucIi  a  manner  jw  to  present  a  most  decided  improvement  over 
previoiLS  editions.  \)t.  Hewitt  is  tlie  leadiiuj  clinical  teacher  on  Diseases  of  Women  in  London, 
and  the  characteristic  attention  paid  to  Diagnrwia  by  him  has  given  his  work  great  j>opnlarity 


18 
HILLIER  (THOMAS),  M.D., 

Physician  to  the  Hospitai  for  Sicl<  Children,  &.c 

A  CLINICAL  TREATISE  ON  THE  DISEASES  OF  CHILDREN. 
Octavo.      Price       .........     ^2.00 

HANDY'S  TEXT-BOOK  OF  ANATOMY  and  Guide  to  Dissec- 
tions for  the  Use  of  Students.     312  Illustrations.     Octavo        .     $3.00 

HOLDEN  (luther),  F.R.C.S. 
HUMAN    OSTEOLOGY,    compri.sing  a  Description  of  the  Bones 

with   Delineations    of  the   Attachments    of  the    Muscles,    &c.     With 

numerous  Illustrations.     Fifth  Edition,  carefully  Revised.    Price,  ^5.50 
HOLDEN'S  MANUAL  OF  DISSECTIONS  OF  THE  HUMAN 

BODY.     Fourth  London  Edition.     With  Illustrations.     Price     $5.50 
LANDMARKS,  MEDICAL  AND  SURGICAL.     Second  Edition. 

Revised  and  Enlarged.      Price     .         .         .         .         ,         .'       $1.00 

HARRIS  (cHAPiN  A.),  M.  D.,  D.  D.  S. 

Late  President  of  and  Professor  of  the  Principles  and  Practice  of  Dental  Suri:ery  in  the  Baltimore  College,  &.c, 

THE  PRINCIPLES  AND  PRACTICE  OF  DENTISTRY.  Tenth 
Revised  Edition.  In  great  part  rewritten,  rearranged,  and  with  many- 
new  and  important  Illustrations.  Including — i.  Dental  Anatomy  and 
Physiology.  2.  Dental  Pathology  and  Therapeutics.  3.  Dental  Sur- 
gery. 4.  Dental  Mechanics.  Edited  by  P.  H.  Austen,  M.D.,  Pro- 
fessor of  Dental  Science  and  Mechanism  in  the  Baltimore  College  of 
Dental  Surgery.  With  nearly  400  Illustrations,  including  many  new 
ones  made  especially  for  this  edition.  Royal  octavo.  Price,  in  cloth, 
^6.50;  in  leather  ........     ^7.50 

This  new  edition  of  Dr.  Harris's  work  has  been  thoroughly  revised  in  all  its  parts  —  more 
80  than  any  previous  edition.  So  great  have  been  the  advances  in  many  branches  of  dentistry, 
that  it  was  found  necessary  to  rewrite  the  articles  or  subjects,  and  this  has  been  done  in  the 
most  efficient  raanuer  by  Professor  Austen,  for  many  years  an  associate  and  friend  of  Dr. 
Harris,  assisted  by  Professor  Gorgas  and  Thomas  S.  Latimer,  M.  D.  The  publishers  feel 
assured  that  it  will  now  be  found  the  most  complete  text-book  for  the  student  and  guide  for 
tlie  practitioner  in  the  English  language. 

SAME  AUTHOR. 
A  DICTIONARY  OF  MEDICAL  TERMINOLOGY,  DENTAL 
SURGERY,  AND  THE  COLLATERAL  SCIENCES.  Fourth  Edition, 
Carefully  Revised  and  Enlarged,  by  Ferdinand  J.  S.  Gorgas,  M.  D., 
D.D.S.,  Professor  of  Dental  Surgery  in  the  Baltimore  College,  &c.,  &c. 
Royal  octavo.     Price,  in  cloth,  ^6.50;  in  leather  .  .         ^7-5° 

The  many  advances  in  Dental  Science  rendered  it  necessary  that  this  edition  should  be 
thoroughly  revised,  which  has  been  done  in  the  most  satisfactory  manner  by  Professor  Gorgas, 
Dr.  Harris's  successor  in  the  Baltimore  Dental  College,  he  having  added  nearly  three  thou- 
sand new  words,  besides  making  many  additions  and  corrections.  The  doses  of  the  more 
prominent  medicinal  agents  have  also  been  added,  and  in  every  way  the  book  has  been  greatly 
improved,  and  its  value  euhancetl  as  a  work  of  reference. 

HABERSHON  (s.  a),  M.  D.,  F.  R.  C.  R, 

Senior  Physician,  Guy's  Hospital. 

ON   DISEASES    OF  THE  ABDOMEN,  STOMACH,  and  Other 

Parts  of  the  Alimentary  Canal.     Third  London  Edition.    Price,  $5.00 

ON  DISEASES  OF  THE  STOMACH  :  The  Varieties  of  Dyspepsia. 

their  Diagnosis  and  Treatment.     Third  Edition.     Octavo        .     ^1.75 


19 

HARDWICH  AND  DAWSON. 

HARDWICH'S  MANUAL  OF  PHOTOGRAPHIC  CHEMISTRY. 

With  Engravings.      Eighth  Edition.      Edited  and  Rearranged   by  G. 
Dawson,  Lecturer  on  Photography,  &c.,  &c.      i2mo    .  .  $2.00 

HARLAN  (geTIrge  c),  M.  D., 

Su  geon  to  Wills'  Eye  Hospital,  &c. 

P:YESIGHT.  and  how  to  care  for  it.     (Vol.  IV.,  Amer- 
ican Health  Primers.)     Cloth.      Price  ....  $0.50 

HEADLAND  (f.  w.),  M.  D., 

Fellow  of  the  Royal  College  of  Physicians,  SiC,  &c. 

ON  the  action  of  medicines  in  the  system.     Sixth 
American  from  the  Fourth  London  Edition.     Revised  and  Enlarged. 
Octavo.     Price      .  .         .         .         .         .         .         .         .     $3.00 

Dr.  Headland's  work  gives  the  only  scientific  and  satisfactory  view  of  the  action  of  medi- 
cine; and  this  not  in  the  way  of  idle  speculation,  but  by  demonstration  and  experiments, 
and  inferences  almost  as  indis|)utab]e  as  demonstration'!.  It  is  truly  a  great  scientific  work 
in  a  small  compass,  and  deserves  to  be  the  hand-book  of  every  lover  of  the  Profession.  It 
has  received  the  approbation  of  the  Medical  Press,  both  in  this  country  and  in  Europe,  and 
is  pronounced  by  them  to  be  the  most  original  and  practically  useful  work  that  has  been 
issued  for  many  years. 

HOFF  (o.),  M.D. 

on  HiEMATURIA  as  a  Symptom  of  Diseases  of  the  Genito-Uri- 

nary  Organs.      Illustrated.      i2mo.      Cloth.      .  .  .  .      $0.75 

HEATH  (CHRISTOPHER),  F.R.C.S.,, 

Surgeon  to  University  College  Hospital,  &c. 

INJURIES  AND  DISEASES  OF  THE  JAWS.  The  Jacksonian 
Prize  Essay  of  the  Royal  College  of  Surgeons  of  England,  1867.  Sec- 
ond Edition,  Revised,  with  over   150  Illustrations.     Octavo.      Price, 

^4-25 

SAME  AUTHOR. 

A  MANUAL  OF  MINOR  SURGERY  AND  BANDAGING,  for 

the  Use  of  House  Surgeons,  Dressers,  and  Junior  Practitioners.     With 

a  Formulae  and  Numerous  Illustrations.      i6mo.        Price  ..     ^2.00 

A  GUIDE  TO  SURGICAL  DIAGNOSIS,  for  Practitioners  and 
Students,      ismo.     Cloth.     Price  .         .         .         .         .     ^1.50 

HAYDEN  (THOMAS),  M.  D., 

Fellow  of  the  King  and  Queen's  College  of  Physicians,  &c.,  &.c. 

THE  DISEASES  OF  THE  HEART  AND  AORTA.  With  8r 
Illustrations.    In  two  volumes,  Of:tavo,  of  over  1200  pages.  Price,     ^6.00 

HUFELAND  (c.  w.),  M.D. 

THE  ART  OF  PROLONGING  LIFE.  Edited  by  Erasmus  Wil- 
son, M.  D.,  F.  R.S.,  &c.     i2mo.     Cloth $1.00 

HAY  (iiioMAs).  M.  D., 

HISTORY  OF  A  CASE  OF  RECURRING  SARCOMATOUS 
TUMOUR  OF  THE  ORlilT  IN  A  CHILD.  With  Three  Full  Page 
Illustrations,  representing  the  Tumour  in  its  Various  Stages.  Price,  jSo.50 


20 
HEWSON  (addinell,)  M.  D. 

Attending  Surgeon  Pennsylvania  Hospital,  &c. 

EARTH  AS  A  TOPICAL  APPLICATION  IN  SURGERY. 
Being  a  full  Exposition  of  its  use  in  all  the  Cases  requiring  Topical 
Applications  admitted  in  the  Surgical  Wards  of  the  Pennsylvania  Hospi- 
tal during  a  period  of  Six  Months.     With  Illustrations.     Price  ^2.50 

HUTCHINSON  (Jonathan),  R  R.  C.  S. 

Senior  Surgeon  to  tfie  London  Hospital. 

ILLUSTRATIONS  OF  CLINICAL  SURGERY.  Consisting  of 
Plates,  Photographs,  Wood-cuts,  Diagrams,  etc.,  Illustrating  Surgical 
Diseases,  Symptoms  and  Accidents,  also  Operations  and  other  Methods 
of  Treatment.  With  Descriptive  Letter-press.  -10  Parts  Bound,  com- 
plete in  itself.     Price,  ^25.00.    Parts  11  and  12  now  ready.    Price,  ^2.50 


HODGE  (hughl.),  M.  D. 

Emeritus  Professor  in  tlie  University  of  Pennsylvania. 

HODGE     ON     FCETICIDE,    OR     CRIMINAL     ABORTION. 
Fourth  Edition.     Price,  in  paper,  30  cents;  in  cloth,  .  $0.50 

HODGE'S  (h.  lenox)  NOTE- BOOK  FOR  CASES  OF  OVARIAN 
TUMORS.     With  Diagrams,  etc.     Price,  .  •       .         .         .  ^0.50 

HOLDEN  (edgar),  A.  M.,  M.  D., 

Of  Newark,  New  Jersey. 
CONTAINING  THREE  HUNDRED  ILLUSTRATIONS. 
THE  SPHYGMOGRAPH.  Its  Physiological  and  Pathological  In- 
dications. The  Essay  to  which  was  awarded  the  Stevens  Triennial 
Prize  in  the  College  of  Physicians  and  Surgeons  in  New  York,  April, 
38.73.  Illustrated  by  Three  Hundred  Engravings  on  Wood.  One  vol- 
lume  octavo.     Price.       .  .  .  .         .  .         .         .     ^2.00 

HOOD  (p.),  M.D. 

A  TREATISE  ON  GOUT,  RHEUMATISM,  AND  THE  ALLIED 
AFFECTIONS.     Crown  octavo.  ^3.50 

JONES  (h.  macnaughton),  M.  D.,  M.  Ch. 

A  PRACTICAL  TREATISE  ON  AURAL  SURGERY.  Illus- 
trated.    i2mo.     Price  .         .         .         .         .         .         .         .^1.50 

JONES   (t.  WHARTON),  F.R.S. 
DEFECTS  OF  SIGHT  AND  HEARING.     Their  Nature,  Causes, 
Prevention,  &c.     Second  Edition.     Price        ...         -     $°-5° 

JONES,  SIEVEKING,  and  PAYNE. 

A  MANUAL  OF  PATHOLOGICAL  ANATOMY.  By  C.  Hand- 
field  Jones,,  M.  D.,  F.  R.  S.,  Physician  to  St.  Mary's  Hospital;  and 
Edward  H.  Sieveking,  M.D.  ,  F.R.C.P.,  Physician  to  St. Mary's  Hos- 
pital. A  New  and  Enlarged  Edition.  Edited  by  J.  F.  Payne,  M.B., 
F  R.C.P.,  Assistant  Physician  and  Lecturer  on  Morbid  Anatomy  at  St. 
Thomas's  Hospital.     With  Numerous  Illustrations.  .  .     ^5.50 


21 
JAMES  (frosser),  M.  D.,  IvI.  R.  C.  P., 

Physician  to  Throat  Hospital. 

SORE  THROAT:  Its  Nature.Varieties.  and  Treatment,  and  its  Con- 
nection with  other  Diseases.  Fourth  Edition.  Colored  Plates.  i2mo. 
Price ^2.25 

JONES'  AURAL  ATLAS. 
AN  ATLAS  OF  DISEASES  OF  THE  MEMBRANA  TYMPANI. 

Being  a  Series  of  Colored  Plates,  containing  62  Figures.  With  appro- 
priate Letter-Press  and  Explanatory  Text  by  H.  McNaughton  Jones. 
M.D.,  Surgeon  to  the  Cork  Ophthalmic  and  Aural  Hospital.  4to 
Cloth'.     Pnce ^^  °° 

KIDD  (josepioTmTd.,  M.  R.  C.  S. 
THE  LAWS  OF  THERAPEUTICS,  or  The  Science  and  Art  of 
Medicine.      121110.      Cloth.      Price ^^-^S 

LONGLEy"(elias). 

Author  of  a  "  Pronouncing  Vocabul  ry  of  Geographical  f.nd  Personal  Names,"  Lc. 

STUDENT'S  POCKET  MEDICAL  LEXICON.  Giving  the  Cor- 
rect Pronunciation  and  Definition  of  all  Words  and  Terms  in  general 
use  in  Medicine  and  the  Collateral  Sciences.  The  Pronunciation  being 
plainly  represented  in  the  American  Phonetic  Alphabet.  With  an 
Appendix,  containing  a  Complete  List  of  Poisons  and  their  Antidotes, 
Abbreviations  used  in  Prescriptions,  and  a  Metric  Scale  of  Doses. 
24nio.    Cloth.    Price,  $1.00  ;  in  Leather,  with  Tucks  and  Pocket,  $1.25 

This  is  an  entirely  new  Medical  Pictionarv,  containing  sojiie  300  compactly  printed 
'Mmo  pa«'-es  very  curefullv  prepared  bv  the  antlior,  who  has  had  much  experience  in  the 
preparation  of  si'inilar  works,  assisted  bv  the  Professors  of  Chemistry  and  of  Botany  in  one 
',f  our  leadinc'  Medical  Colleges.  It  contains  all  medical  terms  in  common  use,  with  their 
pronunciation  and  definition,  without  i)eing  encumbered  with  obsolete  or  useless  words. 
It  is  essentially  new  in  many  of  its  features,  and  fully  brought  up  to  the  present  state  oi 
medical  science.- 

LAWSON  (^eo^e),  F.R.C.S., 

Surgeon  to  the  Royal  London  Ophthalnnic  Hospital. 

DISEASES  AND  INJURIES  OF  THE  EYE,  THEIR  MEDICAL 
AND  SURCICAL  TREATMENT.  Containing  a  Formulary,  Test 
Types,  and  Numerous  Illustrations.      Price       .... 

LEBER  &  ROTTENSTEIN  (drs.). 

DENTAL  CARIES  AND  ITS  CAUSES.  An  Investigation  into 
the  Influence  of  Fungi  in  the  destruction  of  the  Teeth,  translated  by 
'Ihomas  H.  Chandler,  D.M.D  ,  Professor  of  Mechanical  Dentistry  in 
the  Dental  School  of  Harvard  University.  With  Illustrations.  Octavo. 
Price ^1-25 

LEARED  (ARTHUR),  M.D.,  F.R.C.P. 

IMPERFECT  DIGESTION:  ITS  CAUSES  AND  TREATMENT. 
Tlie  Sixth  Edition,  Revised  and  Enlarged.        ....      $1.50 

KOLLMEYER  (a.  h.),  A.  M.,  M.  D. 

Professor  of  Materia  Medica  and  Therapeutics,  Montreal  College, 

CHEMIA  COARTATA  ;  or,  The  Key  to  Modern  Chemistry.  With 
Numerous  Tables,  Tests,  &c.,  &c.     Price,        ....     ^2.25 


22 

LEWIN   (dr.  George). 

Professor  at  the  Fr,-Wilh.  University,  and  Surgeon-in-Chief  of  tlie  Syphilitic  Wards  and  Skin  Diseases  of 

the  Charity  Hospital,  Berlin. 

THE  TREATMENT  OF  SYPHILIS  by  Subcutaneous   Sublimate 

Injections.  With  a  Lithograpliic  Plate  illustrating  the  Mode  and  Proper 
Place  of  administering  the  Injections,  and  of  the  Syringe  used  for  the 
purpose.  Translated  by  Carl  Prcegler,  M.D.,  late  Surgeon  in  the 
Prussian  Service,  and  E.  H.  Gale,  M.D.,  late  Surgeon  in  the  United 
States  Army.     Price       .         .         .         .         .         .         .         .     ;gi.5o 

MASON  (FRANCIS),  F.R.C.S., 

Surgeon  and  Lecturer  on  Anatomy  at  St.  Thonnas'  Hospital,  &c, 

THE  SURGERY  OF  THE  FACE.  With  lOO  Illustrations,  En- 
graved on  Wood,  of  Various  Operations  Performed.      Octavo.     Cloth. 

Price,  $2.25 

MORRIS  ^ii^Y),  F.  R.  C.  S. 

THE  ANATOMY  OF  THE  JOINTS  OF  MAN.  Comprising  a 
Description  of  the  Ligaments,  Cartilages,  and  Synovial  Membranes  ;  of 
the  Articular  Parts  of  Bones,  &c.  Illustrated  by  44  Large  Plates  and 
Numerous  Figures,  many  of  which  are  Colored.     Octavo.     Price,  ^^5.50 

MACNAMARA  (c). 

Surgeon  to  the  Ophthalmic  Hospital,  and  Professor  of  Ophthalmic  Medicine  in  the  Medical  College,  Calcutta, 

MANUAL  OF  THE  DISEASES  OF  THE  EYE.  The  Third 
Edition,  carefully  Revised;  with  Additions,  and  numerous  Colored 
Plates,  Diagrams  of  the  Eye,  many  Illustrations  on  Wood,  Snellen's 
Test  Types,  &c.,  &c.     Price  .         .         .         .         .         .     ^4.00 

MARSH    (SYLVESTER). 

SECTION-CUTTING.  A  Practical  Guide  to  the  Preparation  and 
Mounting  of  Sections  for  the  Microscope  —  special  prominence  being 
given  to  the  subject  of  Animal  Sections.     With  Illustrations.     Cloth. 

Price,  $0.75 

MACKENZIE  (morell),  M.  D., 

Physician  to  the  Hospital  for  Diseases  of  the  Throat,  &c. 

GROWTHS  IN  THE  LARYNX.  Their  History,  Causes,  Symp- 
toms, &c.  With  Reports  and  Analysis  of  One  Hundred  Cases.  With 
Colored  and  other  Illustrations.     Price  .....     ^2.00 

OTHER   WORKS  BY  THE  SAME  AUTHOR. 

THE   LARYNGOSCOPE   IN  THROAT   DISEASES.     With  an 

Appendix  on  Rhinoscopy.  Third  Edition,  Enlarged.  With  New  Il- 
lustrations.    Price  ........ 

THE  DISEASES  OF  THE  THROAT  AND  NOSE.  Including 
The  Pharynx,  The  Larynx,  Trachea,  CEsophagus,  Nose,  Neck,  &c. 
With  numerous  Illustrations.     Preparing. 

DIPHTHERIA.     Its  Nature,  Varieties,  and  Treatment.    Price,  ^o  75 

PHARMACOPGEIA  OF  THE  HOSPITAL  FOR  DISEASES  OF 
THE  THROAT.  .With  One  Hundred  and  Fifty  Formulae  for  Gar- 
gles, &c.,  &c.     Fourth  Edition.     Preparing. 


23 

MEIGS  AND  PEPPER. 

A  PRACTICAL  TREATISE  ON  THE  DISEASES  OF  CHIL- 
DREN. By  J.  Forsyth  Meigs,  M.D.,  Fellow  of  the  College  of  Physi- 
cians of  Philadelphia,  &c.,  &c.,  and  William  Pepper,  M.D.,  Physician 
to  the  Philadelphia  Hospital,  &c.  Sixth  Edition,  thoroughly  Revised 
and  greatly  Enlarged,  forming  a  Royal  Octavo  Volume  of  over  looo 
pages.     Price,  bound  in  cloth,  ^6.00;   leather  .  .  .     ^7.00 

It  is  tiie  most  complete  work  ou  the  subject  ia  our  language.  It  contains  at  once  tlie  re- 
sults of  personal,  au<l  tlie  exjierience  of  others.  Its  quotations  from  the  most  recent  authf)r- 
ities,  at  liome  and  abroad,  are  ample,  and  we  think  tlie  authors  deserve  congratulations  for 
having  jiroduced  a  book  unequalled  for  the  use  of  the  student  and  indispensable  as  a  work 
of  reference  for  the  practitioner.  —  American  Jledical  Journal. 

MEARS  (j.  EwiNc;),  M.  D., 

Demonstrator  of  Surgery  in  Jefferson  Medical  College,  &c, 

PRACTICAL  SURGERY:  Including  Surgical  Dressings.  Bandag- 
ing, Amputation,  &c.,  <S:c.    227  Illustrations.    For  the  use  of  Students. 

Price,  $2.00 

MENDENHALL  (george),  M.D., 

Professor  of  Obstetrics  in  the  Medical  College  of  Ohio,  &.c. 

MEDICAL  STUDENT'S  VADE  MECUM.  A  Compendium  of 
Anatomy,  Physiology,  Chemistry,  the  Practice  of  Medicine,  Surgery, 
Obstetrics,  Diseases  of  the  Skin,  Materia  Medica,  Pharmacy,  Poisons, 
&c.,  &c.  Eleventh  Edition,  Revised  and  Enlarged,  with  224  Illustra- 
tions.    In  cloth $2.00 

MAXSON  (EDWIN  R.),  M.D., 

Formerly  Lecturer  on  the  Practice  of  Medicine  in  the  Geneva  Medical  College,  &c. 

THE  PRACTICE  OF  MEDICINE ^^3.00 

MARSHALL  (john),  F.R.S., 

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24 
MAUNDER  (c.  f.),  F.  R.  C.  S. 

Surgeon  to  the  London  Hospital;  formerly  Dennonstrator  of  Anatomy  at  Guy's  Hospital. 

OPERATIVE  SURGERY.  Second  Edition,  with  One  Hundred 
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MAYS  (THOMAS  J.),  M.  D. 

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Force.      i2mo.     Cloth.     Price       .         .         .         .         •         .     ^1.25 

MARTIN   (JOHN  H.). 

Author  of  Microscopic  Objects,  &c, 

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MEADOWS  (ALFRED),  M.D. 

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Professor  of  Surgery  University  of  Edinburgh. 

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25 

MARSDEN    (ALEXANDER),  M.D. 

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26 

PARKES   (EDWARD  A.),  M.  D., 
Professor  of  Military  Hygiene  in  the  Army  Medical  School,  &c, 

A  MANUAL  OF  PRACTICAL  HYGIENE.       The    Fifth  Revised 

and  Enlarged  Edition,  for  Medical  Ofificers  of  the  Army,  Civil  Medical 
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PAGET  ( JAMES),  F.  R.  S., 

Surgeon  to  St.  Bartholomew's  Hospital,  &c, 

SURGICAL  PATHOLOGY.     Lectures  delivered  at  the  Royal  Col- 
lege of  Surgeons  of  England.     Third  London  Edition,  Edited   and 
Revised  by  William  Turner,   M.  D.     With  Numerous   Illustrations. 
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27 
PARSONS  (CHARLES),  M.  D., 

Honorary  Surgeon  to  the  Dover  Convalescent  Homes,  (Stc,  &.c, 

SEA-AIR  AND  SEA-BATHING.  Their  Influence  on  Health  a 
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PARKER  (langston),  F.  R.  C.  S.  L. 

THE  MODERN  TREATMENT  OF  SYPHILITIC  DISEASES. 
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Analytical  Chemist. 

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28 
RINDFLEISCH   (dr.  edward). 

Professor  of  Pathological  Anatomy,  University  of  Bonn. 

TEXT-BOOK  OF  PATHOLOGICAL  HISTOLOGY.     An  Intro. 

duction  to  the  Study  of  Pathological  Anatomy.  Translated  frum  the 
German,  by  Wm.  C.  Kloman,  M.D.,  assisted  by  F.  T.  Miles,  M.D., 
Professor  of  Anatomy,  University  of  Maryland,  &c.,  &c.  Containing 
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man medical  literature.  What  makes  it  especially  valuable  is  the  fact  that  it  was  originated, 
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Assistant  Physician  and  Teacher  of  Clinical  Medicine  in  the  University  College  Hospital  j  Assistant  Physkian 
Brompton  Consumption  Hospital,  &c. 

THE    THEORY    AND    PRACTICE    OF    MEDICINE.      Third 

American,   from  Fourth  London,   Edition.      Revised    and    Enlarged. 
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REYNOLDS  (j.  russell),  M.  D.,  F.  R.  S., 

Lecturer  on  the  Principles  and  Practice  of  Medicine,  University  College,  London. 

LECTURES   ON   THE   CLINICAL  USES  OF  ELECTRICITY. 

Delivered  at  University  College  Hospital.     Second  Edition,  Revised 
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RYAN    (MICHAEL),  M.  D. 
Member  of  the  Royal  College  of  Physicians, 

PHILOSOPHY  OF  MARRIAGE,  in  its  Social,  Moral,  and  Physi- 
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11 


29 

RADCLIFFE  (charles  bland),  M.D., 

Fellow  of  the  Royal  Ccllege  of  Physicians  of  London,  &c. 

LECTURES   ON    EPILEPSY,    PAIN,    PARALYSIS,   and   other 

Disorders  of  the  Nervous  System.      With  Illustrations.      .  .      $1.50 

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throw  much  lisjht  ujjou  the  Physiology  aud  Pathology  of  the  Nervous  System,  —  Canada 
Medical  Journal, 

ROBERTSON  (a.),  M.D.,  D.D.S. 

A   MANUAL   ON    EXTRACTING    TEETH.     Founded  on    the 

Anatomy  of  the  Parts  involved  in  the  Operation,  the  kinds  and  proper 
construction  of  the  instruments  to  be  used,  the  accidents  likely  to  occur 
from  the  operation,  and  the  proper  remedies  to  retrieve  such  accidents. 
A  New  Revised  Edition.         ....... 

RICHARDSON  (joseph  g.),  M.  D., 

Professor  of  Hygiene  in  Pennsylvania  University. 

LONG  LIFE,  AND  HOW  TO  REACH  IT.  (Vol.  II.,  American 
Health  Primers.)     Cloth.     Price  .         .         .         .         .         $o-5o 

REESE  (JOHN  J.),  M.D., 

Professor  of  Medical  Jurisprudence  and  Toxicology  in  the  University  of  Pennsylvania, 

AN  ANALYSIS  OF  PHYSIOLOGY.  Being  a  Condensed  View 
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Use  of  Students.     Second  Edition,  Enlarged.  .         .         .     ^1.50 

SAME  AUTHOR. 
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RICHARDSON  (joseph),  D.D.S. 

Late  Professor  of  Mechanical  Dentistry,  &c.|  &c. 

A  PRACTICAL  TREATISE  ON  MECHANICAL  DENTISTRY. 

Second  Edition,  much  Enlarged.  With  over  150  beautifully  executed 
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ROBERTS  (lloyd  d.),  M.D., 

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32 
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AMERICAN  HEALTH  PRIMERS. 

Edited  by  W.  W.  KEEN,  LI.  D., 

Fellow  of  the  College  of  FhT/.tidans  of  rhiladclplda;  Surgeon  to 
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This  serips  of  American  Health  rriniprs  ia  prepared  to  (iiffuse  ns  widely  and  cheaply  as  possible. 
unong  all  cIh.-scs,  a  knuwlfdge  of  the  eli-iuentary  {acts  of  Treventive  Medicine,  and  the  bearings  and 
Bpplicatiuiis  of  tlie  l.itest  and  best  researches  in  every  brandi  of  Medical  and  Hygienic  Science.  TUey 
are  ni-t  intemled  (save  jiiciiientiiUy)  to  assist  in  curing  disease,  but  to  teach  people  how  to  talie  care  of 
themselves,  tlieir  children,  pujils,  employees,  etc. 

They  are  written  fiom  an  American  standpoint,  with  especial  reference  to  our  OlimHte,  Sanitiry 
Legislation,  and  Slodes  of  Life;   and  in  these  respects  we  differ  niaterially  frum  other  natimis. 

The  subjects  selected  are  of  vital  and  practical  inijiortance  in  every-d;iy  life,  and  are  treateil  in  as 
popular  a  stylo  as  is  consistent  with  their  nature.  Each  volume,  when  the  Bubject  calls  f.r  it,  is  I'ully 
Illustrated,  so  that  the  text  may  be  clearly  and  readily  understood  by  any  one  heretofure  eiitirelj 
ignorant  of  the  structure  and  functions  of  the  body.  The  object  being  to  lurnish  the  general  or  un- 
Bcientific  reader,  in  a  compact  form  and  at  a  low  price,  reliable  guides  tor  the  prevention  of  disease  and 
the  pieservation  of  b.ith  body  and  mind  in  a  healthy  state. 

The  authors  have  been  selected  with  great  care,  and  on  account  of  special  fitness,  each  for  his  subject, 
by  reason  of  iis  previous  careful  study,  either  privately  or  as  public  teachers. 

Dr.  Keen  has  supervised  the  Series,  us  Kditor;  but  is  not  responsible  for  the  statements  or  opinions 
of  the  individual  authors. 


I.  Hearinfff  and  How  to  Keep  It.      With  Illustrations.      By 

Cha.s.  H.  Burnett,  M.  D.,  of  Philadelphia,  Consulting  Aurist  to  the 
Pennsylvania  Institution  for  the  Deaf  and  Dumb,  Aurist  to  the  Presby- 
terian Hospital,  etc. 

II,  Long  life,  and  Hoiv  to  Heach  It.     By  J.  G.  Richardson, 

M.  D.,  of  Philadelphia,  Professor  of  Hygiene  in  the  University  of 
Pennsylvania,  etc. 

III,  The  Smnnier  and  its  Diseasen.    By  James  C.  Wilson, 

M.I).,  of  Philadelphia,  Lecturer  on  Physical  Diagnosis  in  Jeflerson 
Medical  College,  etc. 

IV.  Eyesight f  and  How  to  Care  for  It,    With  Illustrations.    By 

George  C.  Harlan,  M.  D.,  of  Philadelphia,  Surgeon  to  the  Wills  (Eye) 
Hospital. 
F.  The  Throat  and  the  Voice.     With  Illustrations.     By  J.  Solis 
Cohen,  M.  D.,  of  Philadelphia,  Lecturer  on  Diseases  of  the  Throat  in 
Jefferson  Medical  College. 

VI,  The  Winter  and  its  Dangers,     By  Hamilton  Osgood,  M.  D., 

of  Boston,  Editorial  Staff  Boston  Medical  and  Surgical  Journal. 

VII,  The  Mouth  and  the  Teeth,    With  Illustrations.    By  J.  W. 

White,  M.  D.,  I).  D.  S.,  of  Philadelphia,  Editor  of  the  Dental  Cosmos. 

VIII,  lirain  Work  and  Overwork,    By  H.  C.  Wood,  Jr.,  ]\I.  D., 

of  Philadelphia,  Clinical  Professor  of  Nervous  Diseases  in  the  University 
of  Pennsylvania,  etc. 
JX.  Our  Homes,    With  Illustrations.    By  Henry  Hartshorne,  M.  D., 
of    Philadelphia,    formerly    Professor    of    Hygiene    in   the    University    of 
Penn.sylvania. 

X,  The  Skin  in  Health  and  Hisea.se,    By  L.  D.  Bulkley,  M.D., 

of  New  York,  Physifiiin  to  the  Skin  I)ej)artmeut  of  the  Demilt  Dispensary 
and  of  the  New  York  Hospital. 

XI,  Sea  Air  and  Sea  liathing.     By  John  H.  Packard,  M.  D., 

of  Philadelphia,  Surgeon  to  the  Episcopal  Ilo.spital. 

XII,  School andlndustrial Hygiene,    ]iy  I). F. LrN(  oln, M. D., 

of  Boston,    Mass.,    Chairman    Department   of   Health,    American    Social 

Science  Association. 
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